Northwest Micro Mineral Study Group

MICRO PROBE

FALL, 2008 VOLUME X, Number 8

FALL MEETING ...... VANCOUVER, WASHINGTON

November 8, 2008 9:00 am to 5:00 pm

Clark County P. U. D. Building 1200 Fort Vancouver Way Vancouver, Washington

Come find out what everyone has been up to this summer. Bring your microscopes and something for the free table to share with others. There will be plenty of room and ample time to check out all the new things that people have to brag about. We will have our usual brief business meeting in the afternoon, a discussion of future articles, and our update session on the status of localities.

No guest speaker has been planned, but we will N be showing pictures of the new twins from Lemolo Lake, as well as of other choice pieces from the Northern California meeting in July. If you have digitals or slides of mineral specimens or collecting localities, this would be a perfect time to share them with the group. We will have projectors and a screen waiting. I5 The kitchen area is again available and we will plan on sharing lunch together. We will provide meat, cheese, bread, lettuce, tomatoes, mayo and mustard for sand-wiches as well as coffee, PUD Mill Plain Blvd. tea, cider, and cocoa. Members need to bring some sides, ie, salads, chips, desserts and anything else that they would like to have to Park Ft. Vancouver Way munch on. Washington In the evening, many of us plan to go to a local Interstate buffet restaurant, so please plan to join us if you Bridge Columbia River can. Oregon

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Garnets at Summit Rock

Don Howard

“I never heard of that!” you say? That was my first reaction as well. But there it was in a box of stuff from Summit Rock, in little itty bitty cardboard boxes that verified what was printed on the folded label: Dave Yeomans. It was stuff he had collected years ago, moved after his death into the hands of Fred Devito, and now at last appearing on the free table at the Northern California Mineralogical Association meeting at El Dorado, California in July, 2008. And all the little label said was „garnet‟.

The rock was clearly the right stuff for Summit Rock: the heavily oxidized material with rounded stubs that had once been enstatite, grayish blades of ilmenite, lots of prisms of plagioclase, a few aegirine needles, and a smattering of while apatite crystals laying like jackstraws in the bottom of the cavities. And among them were very obvious dodecahedral crystals, some with rounded corners and edges, others sharper but with a dusky coating of something siliceous. The color varies from a clear golden brown to much darker, often streaked through a single individual. Their identity as garnet was obvious.

Which garnet? The EDAX attachment to the SEM quickly gives an answer: silicate with a little manganese and only the barest hint of aluminum. Andradite. And that makes sense, because aluminum minerals, except for the feldspar, are in short supply at Summit Rock. The manganese could be divalent and substitute at the calcium site, or it could be trivalent and substitute for the ferric iron. In neither case would there be enough to make this anything other than a clear example of andradite.

We usually think of garnets as occurring in metamorphic rock, in schists and limestones that have been heated and altered from sediments. But garnets can be formed in primary environments too, directly from the vapor phase. I think of the beautiful spessartine from Ruby Mountain, Colorado.

So we chalk up another mineral to look for in our Summit Rock specimens. Thank you, Dave Yeomans, for recognizing and noting in passing this interesting material.

A dodecahedral crystal of Andradite, showing slightly rounded edges and etched faces. This crystal is nearly black, but others are a golden brown. The surrounding material is mainly plagioclase and the stumps of oxidized enstatite and ilmenite.

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Pseudobrookite Twins from the Lemolo Lake Quarry

Don Howard and Kent England

Pseudobrookite was originally named in 1878 for material found at Uroiu, Transylvania, Romania. It is a high temperature mineral, usually formed directly from heated gases in igneous rock. For this reason, there are only a limited number of occurrences worldwide. Fortunately, it is fairly common in the rhyolites of the Thomas Range, Utah, so that it is familiar to collectors in the United States. The of pseudobrookite is orthorhombic, the most common form being lathlike needles elongated along the c-axis. Most crystals are black in color, with a submetallic luster. Chemically, the composition is a ferric titanium oxide, Fe2TiO5 , but many analyses show excess titanium oxide. This is thought to be due to inclusions of rutile, but because most crystals are opaque except on the thinnest edges, the inclusions are not generally visible. The blades have well-developed {100} faces that are usually striated parallel to the c- axis. Such striations in minerals are commonly caused by twinning. Considerable consideration for this was put forward during the 1920‟s, and a number of twin planes of the form {hk0} were proposed. But a lack of truly twinned crystals to date has left the matter of twinning in pseudobrookite to be considerably in doubt. Pseudobrookite is reported to occur with enstatite and apatite at Red Cone in Crater Lake National Park, and is found very sparingly on oxidized ilmenite in the cavities at Summit Rock just to the north. But the most collectable material has come from Lemolo Lake, where it forms dark blood-red blades along the bottom margin of the flow exposed along the spillway to the dam. Most of these blades are clear enough to see that there are no inclusions of rutile present. The forms are very simple, with large {100} faces edged by {010} or {210} and terminated by either {101} or {301}. The {100} faces are very smooth and shiny and seldom show any striations at all. That is why it came as a surprise to find so many twinned pseudobrookite crystals, and not just one type of twin, but a bewildering variety of twinning angles present. The twins were found along the margins of a boulder in the west end of the quarry that was originally collected in 1982 and 1983. This is the same boulder that has produced interesting „cyclic twins‟ of enstatite (see accompanying article). Though this particular boulder shows the characteristic contact with the scoria-like flow beneath it, there are considerable differences from the flow exposed along the spillway, in which most of the interesting minerals reported so far have occurred. The cavities in this boulder show primarily three minerals: enstatite, pseudobrookite, and tridymite, with ilmenite crystals conspicuously absent. Extensive twinning is present in all three minerals. The color of the enstatite is yellow rather than the more tan color of those found along the spillway. Though it is possible this rock comes from a different flow, it is more likely from a different region of the same flow with slightly different chemistry conditions present. While most of the twins observed have a composition plane of the form {hk0}, one surprising kind of twin was found with the composition plane {101}. Several examples were observed, and photographs taken looking down the b axis to be able to measure the angle (see insert in the diagram below). However, in at least one case, one member of the twin was terminated by the {301} planes, and it was observed that the {301} of one was very nearly parallel to the {100} of the other by observing the simultaneous reflections from the illuminator. Most of the twins are simple contact twins, but one example of a penetration twin of this type has 4

Contact twin on (101), viewed in the a-b plane. The termination faces are also {101} for both crystals.

(101)

______also been observed, though it was in a position difficult to photograph. The rest of the twins observed all involve rotations about the c-axis. Photographs were taken parallel to that axis of a number of examples, and the angles were measured from them. Only those cases are reported where two or more of the same intercrystal angles were found, in order to avoid any accidental parallel growths. One trouble in identifying just which composition LATTICE PARAMETERS planes are involved in the twinning comes from the fact FOR PSEUDOBROOKITE that the a and b cell dimensions are very nearly the same. a = 9.797 A For the most common twin type, that on {110}, there is no b = 9.981 A problem; the crystals are only about 1o from being exactly c = 3.370 A perpendicular. For the other cases, we have calculated the angles for a variety of low-index planes and taken the ones that come closest to the measured values. Generally, only a couple of degrees separate the candidates, so it is possible that other composition planes could be involved beyond the ones we have identified. Many of these pseudobrookites show penetration twinning, so in the diagram on the next page, we have depicted each case as a penetration twin. The insets show a typical example for each composition plane. We summarize in the table below the types of twins observed. Only those cases have been included where two or more examples could be found and photographed of the same intercrystal angles. Very low angle twins, though present, have not been analyzed and included because of difficulty of determining angles with sufficient accuracy to be able to assign a composition plane, which would have had to have some very high indices. ______

Composition Intercrystal angle Plane Calculated Observed

Summary of the {101} 41.7o 41.5+0.5o observed types {110} 88.9o 88.5+0.5o of twinning in {430} 72.7o 72+1o pseudobrookite {210} 54.0o 54.5+0.5o from Lemolo Lake. {310} 36.2o 36+1o ______5

(110) (430)

(210) (310)

Four types of twinning around the c-axis, employing four different composition planes. The diagrams show only {100} and {010} side prisms, but the examples in the insets show {210} as well as {100} and {010} sides. All views are in the a-b plane looking parallel to the c-axis. ______

A hint as to what is going on here comes from other minerals present. This is the first place that filiform ilmenite was found, as black needles at the contact where this layer flowed over a scoria layer. The presence of a filiform mineral suggests that catalyzed growth was occurring in the heated lava. Probably the catalyzed growth was not limited to the ilmenite. Indeed, a filamentary crystal of pseudobrookite has been observed growing out of a much

A needle-like pseudobrookite crystal growing from the end of a more normal, equant one.

6 sturdier pseudobrookite crystal. The needle is elongated along the c-axis, and is therefore not a filiform in the strict usage of the term, but it could very well have formed in a similar process. So too could thin needles of enstatite. In both cases, the needles could have formed the nucleus from which thicker crystals then grew by more conventional means. Such a nucleus could be responsible for the cyclic enstatite twins mentioned in the accompanying article. Needles of pseudobrookite, oriented along the c-axis, could also have spawned the twins reported here, most of which seem to involve rotations about c . Material formed during catalyzed growth is often not very well crystallized, and subsequent recrystallization could have produced just the wide variety of composition planes we are observing here, all with a common axis. Since catalyzed growth requires rather special conditions, this could also explain why we are observing such a wealth of twins of several minerals limited to a particular place along a rather extensive flow. Things proved to be just right at this particular place to form the types of twins that have been speculated about but never observed until now.

REFERENCES 1. Palache, C., Berman, H., & Frondel, C., The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, (7th edition), John Wiley & Sons, Vol. 1, pg 736-738, (1944). 2. Gaines, R.V., Skinner, H.C.W., Foord, E.E., Mason, B., & Rosenzweig, A., Dana’s New Mineralogy, (8th edition), John Wiley & Sons, pg 1294, (1997). 3. For a more complete discussion of the mineralogy of Lemolo Lake see the following developing articles: The Microprobe, V9#7 pg 3-13; V9#9 pg 3-4; V10#2 pg 8-10; V10#4 pg5-7; V10#7 pg6-7.

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Enstatite Twins from the Lemolo Lake Quarry

Don Howard and Kent England

Small cavities that came from a large boulder near the west end of the quarry pit at Lemolo Lake, Douglas Co., Oregon1 have produced interesting „cyclic twins‟ of enstatite as well as several types of twins in pseudobrookite. While most of the large rocks present along the banks of the spillway originated in the flow exposed on the south side of the spillway, rocks in the quarry may have come from one of several flows. This particular large boulder shows considerable differences from the flow exposed along the spillway, in which most of the interest- ing minerals reported so far have occurred. The cavities in this boulder show primarily three minerals: enstatite, pseudobrookite, and tridymite, with ilmenite crystals conspicuously absent. Extensive twinning is present in all three minerals. The color of the enstatite is yellow rather than the More tan color of those found also the spillway. Twinning in enstatite has been observed pre- viously. These include stellate twins on {201} and Multiple twin of enstatite, Lemolo Lake Quarry. 7 lamellar twins on {014}.2 In the present material from the Lemolo Lake quarry, the composition plane is instead {031}. Calculating from the accepted lattice parameters for enstatite, this plane makes an angle of 29.6o with the c-axis. Thus neighboring members are less than 1o from the ideal 60o for the formation of sixlings. Multiple twinning is indeed observed, as can be seen in the illustration above. The of enstatite at Lemolo Lake consists of a large (100) face boardered by {210} edges. The terminations are mostly {111} and {011} faces, with occasionally a very tiny top bevel of {101} or side bevel of {021}. The (011) face makes an angle of 59.6o with the c-axis, so the major part of the terminations of neighboring members of a group are within less than 2o of alignment. In the illustration, the individuals are well separated, but on some groups the spaces between become nearly completely filled, giving the appearance of a single face with a slightly bent edge. The striations, which commonly are present and run parallel to the c-axis, clearly show the presence of twinning. The incidence of twins in this rock is quite high. The cavities in which the enstatite occurs are small, generally only a few millimeters across, but may show several twinned groups each. One particularly interesting group consists of two pairs of twins at right angles to each other possessing one [013] axis in common. This could be an example of twinning on {331}, which would leave the {100} faces 890 apart, but is probably more an indication that the twins are growing from a nucleus in the form of a filament whose symmetry is closely related to [013] direction in the bulk enstatite structure, but that starts out with tetragonal symmetry. Subsequent growth does not favor tetragonal symmetry, and the system reverts to orthorhombic symmetry overall, leaving a line defect along the original filament that is resolved by forming defect planes, either {031} in the case of pairs or {331} with further defects in the case of the set of four. The nature of a nucleating center that would give rise to the cyclic sixlings is not at all clear.

Schematic drawing of twinning in enstatite on the {031} planes (broken lines). Three individuals shown bounded by {010} and terminated by {011}.

REFERENCES 1. For a more complete discussion of the mineralogy of Lemolo Lake see the following developing articles: The Microprobe, V9#7 pg 3-13; V9#9 pg 3-4; V10#2 pg 8-10; V10#4 pg5-7; V10#7 pg6-7. 2. Gaines, R.V., Skinner, H.C.W., Foord, E.E., Mason, B., & Rosenzweig, A., Dana’s New Mineralogy, (8th edition), John Wiley & Sons, pg 1294 (1997).

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Some Locations in Montana Part 3 - Eastern Montana - North

Larry B. French HC 46 Box 7204 Miles City, MT 59301

The geology of the northern part of eastern Montana consists mainly of Mesozoic sedimentary rocks. These are replaced by Tertiary sedimentary rocks in the north eastern section. Quaternary glacial deposits cover some of the area. Interspersed across the western section are small alkalic intrusions of Tertiary age. Most are associated with these intrusions either as primary or secondary minerals. Zeolites are also present, in very small amounts, in bentonite deposits. The following is a list of occurrences gathered from a review of geologic literature and the specimens in the Montana Mineral Museum (MTMM) at Montana Tech.

Analcime Blaine County: Igneous rocks, Bearpaw Mountains (Tureck-Schwartz & Hyndman, 1991; Tureck-Schwartz, 1992), Cleveland quadrangle (Schmidt and others, 1964), Lloyd quadrangle - euhedral crystals in trachyte and mafic flows, also alteration mineral (Schmidt and others, 1961), Maddux quadrangle - eudhedral crystals and weathering product (Bryant and others, 1960), Rattlesnake quadrangle - phenocrysts and accessory mineral (Hearn and others, 1964), Snake Butte (Leppert, 1985), Missouri River diatremes (Hearn, 1989c; Irving & Hearn, 2003), Haystack Butte (Hearn, 1988).

Chouteau County: Igneous rocks, Highwood Mountains (Weed & Pirsson, 1895; Pirsson, 1905a; Larsen & Buie, 1933; Larsen, 1940, 1941; Buie, 1941; Larsen and others, 1941b; Larsen and others, 1941a; Woods, 1974; Gupta & Yagi, 1980; O'Brien and others, 1988; McCallum and others, 1989; Irving & McCallum, 1991; O'Brien and others, 1991), Square Butte laccolith (Hurlbut, 1939; Beall, 1972; Helm, 1992), Shonkin Sag laccolith (Osborne & Roberts, 1931; Barksdale, 1933), East Peak and Middle Peak stocks (Burgess, 1941), Round Butte laccolith - questionable identification (Liptak, 1984), Big Sag dikes (Irving & Hearn, 2003).

Hill County: Igneous rocks, Bearpaw Mountains (Hearn, 1989a; Tureck-Schwartz & Hyndman, 1991; Tureck-Schwartz, 1992; MacDonald and others, 1992) - near the head of Big Sandy Creek in vermiculite prospect (Heinrich, 1948, 1949; Pecora, 1962; Hearn, 1989a) - old CCC quarry along Beaver Creek - euhedral crystals up to 25 mm (Pecora & Fisher, 1946; Hearn, 1989a; Tschernich, 1992; French, 2003) - Rocky Boy stock (Shank, 1993), Boxelder laccolith (Pecora, 1941; Kuhm, 1983), Bullhook Butte (Weed & Pirsson, 1896a), Centennial Mountain (Hearn, 1989a).

Chabazite Chouteau County: Igneous rocks, Shonkin Sag laccolith (Barksdale, 1933; Hurlbut, 1939; Edmond, 1980), Square Butte laccolith (Hurlbut, 1939).

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Clinoptilolite Blaine County: Sedimentary rocks, near Turner and Harlem - present in bentonite beds in the Bearpaw Shale (Berg, 1969; Sheppard, 1976), northeast of Chinook - Bearpaw Shale - in bentonite beds (Berg, 1969), west of Hays - Bearpaw Shale - trace in bentonite beds (Berg, 1969), northwest of Harlem - Bearpaw Shale - in bentonite beds (Berg, 1969).

Chouteau County: Sedimentary rocks, near Big Sandy - Hell Creek (Wasatch?) Formation (Berg, 1969; Vine & Tourlelot, 1970; Sheppard, 1976).

Phillips County: Sedimentary rocks, southwest of Dodson - Bearpaw Shale - in bentonite beds (Berg, 1969), south of Hays - Mowry Shale - in bentonite beds (Berg, 1969).

Roosevelt County: Sedimentary rocks, northeast of Brockton - Fort Union Formation - trace in bentonite beds (Berg, 1969).

Sheridan County: Sedimentary rocks, southwest of Antelope - Fort Union Formation - in bentonite beds (Berg, 1969; Sheppard, 1976).

Valley County: Sedimentary rocks, near Opheim - Hell Creek Formation - trace in bentonite beds (Berg, 1969), southwest of Glasgow - Bearpaw Shale - trace in bentonite beds (Berg, 1969).

Heulandite Blaine County: Igneous rocks, Maddux quadrangle - locally common - green colored (Bryant and others, 1960).

Hill County: Igneous rocks, Boxelder laccolith (Pecora, 1941).

Pondora County: Sedimentary rocks, scattered locations - Colorado Shale (Cobbin, 1955).

Natrolite Blaine County: Igneous rocks, Lloyd quadrangle - alteration mineral, often fibrous (Schmidt and others, 1961), Maddux quadrangle - fibrous alteration product (Bryant and others, 1960), Rattlesnake quadrangle - alteration product in accessory mineral (Hearn and others, 1964), Snake Butte (Leppert, 1985; MTMM #17070), Missouri River diatremes (Hearn, 1989c; Irving & Hearn, 2003), Haystack Butte (Hearn, 1988).

Chouteau County: Igneous rocks, Highwood Mountains (Pirsson, 1905a; Larsen & Buie, 1933; Larsen, 1941; Larsen and others, 1941a; McCallum and others, 1989; Irving & McCallum, 1991; O'Brien and others, 1991), Shonkin Sag laccolith (Osborne & Roberts, 1931; Hurlbut, 1939; Barksdale, 1933, 1952), Square Butte laccolith (Weed & Pirsson, 1895; Hurlbut, 1939; Beall, 1972; Kendrick, 1980b), Shonkin and Middle Peak stocks (Burgess, 1941), Round Butte laccolith (Liptak, 1984), near Warrick - radiating needles up to 12 cm long by 1 to 5 mm wide (Tschernich, 1992).

Hill County: Igneous rocks, Bearpaw Mountains (Hearn, 1989a), Boxelder laccolith (Pecora, 1941), Centennial Mountain (Hearn, 1989a).

Phillipsite Chouteau County: Igneous rocks, Highwood Mountains (Woods, 1974).

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Stilbite Chouteau County: Igneous rocks, Shonkin Sag laccolith (Osborne & Roberts, 1931; Barksdale, 1933; Hurlbut, 1939; Edmond, 1980), Square Butte laccolith (Hurlbut, 1939).

Thomsonite Blaine County: Igneous rocks, Lloyd quadrangle - accessory mineral and an alteration product (Schmidt and others, 1961).

Chouteau County: Igneous rocks, Highwood Mountains (Larsen, 1941; Larsen and others, 1941a), Shonkin Sag laccolith (Barksdale, 1952; Edmond, 1980), Square Butte laccolith (Beall, 1972).

Hill County: Igneous rocks, Bearpaw Mountains, old CCC quarry along Beaver Creek (Pecora & Fisher, 1946; Hearn, 1989a; Tschernich, 1992; French, 2003), Boxelder laccolith (Pecora, 1941).

Unknown Zeolites Blaine County: Igneous rocks, Snake Butte (Leppert, 1985), intrusion near Lloyd (Weed & Pirsson, 1896b).

Chouteau County: Igneous rocks, Highwood Mountains (Pirsson, 1905a; Buie, 1941; Larsen and others, 1941a; Woods, 1974) - masses over 100 pounds (Larsen, 1941), Lost Lake laccolith (Hurlbut, 1939), Cowboy Creek laccolith (Hurlbut, 1939), Shonkin Sag laccolith (Osborne & Roberts, 1931; Barksdale, 1933; Hurlbut, 1939; Nash, 1970; Gupta & Yagi, 1980; Edmond, 1980; Nash & Monson, 1987; Hyndman and others, 1989), Middle Peak Stock (Burgess, 1941), Square Butte laccolith (Weed & Pirsson, 1895; Hurlbut, 1939; Kendrick, 1980b; Hirsch & Hyndman, 1985; Helm, 1992), Round Butte laccolith (Liptak, 1984), Haystack Butte (Irving & Hearn, 2003).

Hill County: Igneous rocks, Bearpaw Mountains (Hearn, 1989a) - Boxelder laccolith (Kuhm, 1983) - head of Big Sandy Creek (Pecora, 1962) - Beaver Creek area (Hearn, 1989a), Centennial Mountain (Hearn, 1989a).

Phillips County: Igneous rocks, Little Rocky Mountains, Zortman aln”ite dike (Irving & Hearn, 2003).

References

Barksdale, J. D., 1933, The Shonkin Sag laccolith: American Journal of Science, 5th Series, v. 33, p. 321-359.

Barksdale, J. D., 1952, Pegmatite layer in the Shonkin Sag laccolith, Montana: American Journal of Science, v. 250, p. 705-720.

Beall, J. J., 1972, Pseudo-rhythmatic layering in Square Butte alkali-gabbro laccolith: American Mineralogist, v. 57, p. 1294-1302.

Berg, R. B., 1969, Bentonite in Montana: Montana Bureau of Mines and Geology Bulletin 74, 34 p.

Bryant, B., Schmidt, R. G., and Pecora, W. T., 1960, Geology of the Maddux quadrangle Bearpaw Mountains, Blaine County, Montana: U. S. Geological Survey Bulletin 1081-C, p. 91-116.

Buie, B. F., 1941, Igneous rocks of the Highwood Mountains, Montana Part III dikes and related intrusions: Geological Society of America Bulletin, v. 52, p. 1753-1808. 11

Burgess, C. H., 1941, Igneous rocks of the Highwood Mountains, Montana: Part IV, The stocks: Geological Society of America Bulletin, v. 52, p. 1809-1828.

Cobbin, W. A., 1955, Cretaceous rocks of northwest Montana: 6th Annual Field Conference, Billings Geological Society, Billings, p. 107-119.

Edmond, C. L., 1980, Magma immiscibility in the Shonkin Sag laccolith, Highwood Mountains, central Montana: Missoula, University of Montana, M. S. thesis, 90 p.

French, L. B., 2003, Minerals from the C. C. C. Quarry, Beaver Creek, Hill County, Montana: Micro Probe, Vol. IX, No. 7, p. 18-20.

Gupta, A. K., and Yagi, K., 1980, Petrology and genesis of leucite-bearing rocks: Springer-Verlag, New York, 252 p.

Hearn, B. C., Jr., 1988, Alkalic ultramafic magmas in north-central Montana, U. S. A., genetic connections of alnoites, kimberlites, and carbonatites: in Kimberlites and related rocks, Volume I, Their composition, occurrence, origin, and emplacement, Australian Journal of Earth Science Special Publication 14, p. 109-119.

Hearn, B. C., Jr., 1989a, Bearpaw Mountains, Montana: in Montana High Potassium Igneous Province, 28th International Geological Congress Field Trip Guidebook T346, American Geophysical Union, p. 51-61.

Hearn, B. C., Jr., 1989c, Missouri River diatremes, Montana: in Montana High Potassium Igneous Province, 28th International Geological Congress Field Trip Guidebook T346, American Geophysical Union, p. 63-73.

Hearn, B. C., Jr., Pecora, W. T., and Swadley, W. L., 1964, Geology of the Rattlesnake quadrangle Bearpaw Mountains, Blaine County, Montana: U. S. Geological Survey Bulletin 1181-B, 66 p.

Heinrich, E. Wm., 1948, Pegmatite mineral deposits in Montana: Montana Bureau of Mines and Geology Memoir 28, 56 p.

Heinrich, E. Wm., 1949, Pegmatites of Montana: Economic Geology, v. 94, p. 307-335.

Helm, C. T., 1992, Magmatic differentiation of Square Butte laccolith, central Montana alkalic province: Missoula, University of Montana, M. S. Thesis, 106 p.

Hirsch T. L., and Hyndman D. W., 1985, Evolution of Square Butte Laccolith, eastern Highwood Mountains, Montana: Northwest Geology, v. 14, p. 17-31.

Hurlbut, C. S., Jr., 1939, Igneous rocks of the Highwood Mountains, Montana, Part I the laccoliths: Geological Society of America Bulletin, v. 50, p. 1043-1112.

Hyndman, D. W., Alt., D., and Tureck-Schwartz, K., 1989, Shokin Sag and Square Butte laccoliths, Montana: in Montana High Potassium Igneous Province, 28th International Geological Congress Field Trip Guidebook T346, American Geophysical Union, p. 37-47.

Irving, A. J., and Hearn, B. C., Jr., 2003, Montana field trip guidebook, prepared for 8th International Kimberlite Conference, Victoria, British Columbia, Canada, 44 p.

Irving, A. J., and McCallum, I. S., 1991, Eocene potassic magmatism in the Highwood Mountains: Petrology, geochemistry, and tectonic implications: Journal of Geophysical Research, v. 96, n. B8, p. 13,237-13,260.

Kendrick, G. C., 1980b, Magma immiscibility in the Square Butte laccolith of central Montana: Missoula, University of Montana, M. S. Thesis, 90 p.

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Kuhm, P. W., 1983, Magma immiscibility in the Box Elder laccolith, of north-central Montana: Missoula, University of Montana, M. S. Thesis, 86 p.

Larsen, E. S., 1940, Petrographic province of central Montana: Geological Society of America Bulletin, v. 51, p. 887-948.

Larsen, E. S., 1941, Igneous rocks of the Highwood Mountains, Montana, Part II extrusive rocks: Geological Society of America Bulletin, v. 52, p. 1733-1752.

Larsen, E. S., and Buie, B. F., 1933, Potash analcime from the Highwood Mountains of Montana: American Mineralogist, v. 28, n. 12, p. 837-849.

Larsen, E. S., Hurlbut, C. S. Jr., Buie, B. F., and Burgess, C. H., 1941a, Igneous rocks of the Highwood Mountains, Part VI, Mineralogy: Geological Society of America Bulletin, v. 52, p. 1841-1856.

Larsen, E. S., Hurlbut C. S., Jr., Burgess, C. H., and Buie, B. F., 1941b, Igneous rocks of the Highwood Mountains, Montana, Part VII, Petrology: Geological Society of America Bulletin, v. 52, p. 1857-1868.

Leppert, D. E., 1985, Differentiation of shonshonitic magma at Snake Butte, Blaine County, Montana: Missoula, University of Montana, M. S. Thesis, 121 p.

Liptak, A. R., 1984, Geology and differentiation of the Round Butte laccolith, central Montana: Missoula, University of Montana, M. S. Thesis, 49 p.

MacDonald, R., Upton, B. G. J., Collerson, K. D., Hearn, B. C., and James, D., 1992, Potassic mafic lavas of the Bearpaw Mountains, Montana: mineralogy, chemistry and origin: Journal of Petrology, v. 33, n. 2, p. 305-346.

McCallum, S., O'Brien, H. E., and Irving, A. J., 1989, Geology of the Highwood Mountains, Montana: a survey of magma types and sources: in Montana High Potassium Igneous Province, 28th International Geological Congress Field Trip Guidebook T346, American Geophysical Union, p. 23-29.

Nash, W. P., 1970, Shonkin Sag laccolith, Montana: I mafic minerals and estimates of temperature, pressure, fugacity, and silica activity: Contributions to Mineralogy and Petrology, v. 25, n. 4, p. 241-269.

Nash, W. P., and Monson, L. M., 1987, Shonkin Sag laccolith; a differentiated alkaline intrusion, Highwood Mountains, Montana: in Geological Society of America Field Guide No. 2, Rocky Mountain Section, p. 41-44.

O'Brien, H. E., Irving, A. J., and McCallum, I. S., 1988, Complex zoning and resorption of phenocrysts in mixed potassic mafic magmas of the Highwood Mountains, Montana: American Mineralogist, v. 73, n. 9-10, p. 1007-1024.

O'Brien, H. E., Irving, A. J., and McCallum, I. S.,1991, Eocene potassic magmatism in the Highwood Mountains, Montana: petrology, geochemistry, and tectonic implications: Journal of Geophysical Research, v. 96, n. B8, p, 13,237-13,260.

Osborne, F. F., and Roberts, E. J., 1931, Differentiation in the Shonkin Sag laccolith, Montana: American Journal of Science, 5th series, v. 22, p. 331-353.

Pecora, W. T., 1941, Structure and petrology of the Boxelder laccolith, Bearpaw Mountains: Geological Society of America Bulletin v. 52, p. 817-854.

Pecora, W. T., 1962, Carbonatite problem in the Bearpaw Mountains, Montana: in Petrographic Studies a volume in honor of A. F., Buddington, Geological Society of America, p. 83-104.

Pecora, W. T., and Fisher, B., 1946, Drusy vugs in a monzonite dike, Bearpaw Mountains, Montana: American Mineralogist, v. 31, p. 370-385.

13

Pirsson, L. V., 1905a, Petrology and geology of the igneous rocks of the Highwood Mountains, Montana: U. S. Geological Survey Bulletin 237, 208 p.

Schmidt, R. G., Pecora, W. T., Bryant, B., and Ernst, W. G., 1961, Geology of the Lloyd quadrangle Bearpaw Mountains, Blaine County, Montana: U. S. Geological Survey Bulletin 1081-E, p. 159-188.

Schmidt, R. G., Pecora, W. T., and Hearn, B. C., Jr., 1964, Geology of the Cleveland quadrangle Bearpaw Mountains, Blaine County, Montana: U. S. Geological Survey Bulletin 1141-P, 26 p.

Shank, S. G., and Eggler, D. H., 1991, Petrology and geochemistry of the Rocky Boy stock, Bearpaw Mountains, Montana: evolution of shonkinite and monzonite magmas: in Guidebook of the Central Montana Alkalic Province; Geology, Ore Deposits, and Origin: Montana Bureau of Mines and Geology Special Publication 100, 137-140.

Sheppard, R. A., 1976, Zeolites in sedimentary deposits of the northwestern United States - potential industrial minerals: in Eleventh Industrial Minerals Forum, Montana Bureau of Mines and Geology Special Publication 74, p. 70-84.

Tschernich, R. W., 1992, Zeolites of the World: Geoscience Press Inc., Phoenix, Arizona, 563 p.

Tureck-Schwartz, K., 1992, The association of alkalic and subalkalic rocks in the Bearpaw Mountains, Montana: Missoula, University of Montana, M. S. Thesis, 160 p.

Tureck-Schwartz, K., and Hyndman, D. W., 1991, High potassium igneous rocks of the Bearpaw Mountains north- central Montana: in Guidebook of the Central Montana Alkalic Province; Geology, Ore Deposits, and Origin: Montana Bureau of Mines and Geology Special Publication 100, p. 111-120.

Vine, J. D., and Tourelot, E. B., 1970, Priliminary geochemical and petrographic analysis of lower Eocene fluvial sandstones in the Rocky Mountain region: in 22nd Annual Field Conference, Wyoming Geological Association Guidebook, p. 251-263.

Weed, W. H., and Pirsson, L. V., 1895, Highwood Mountains of Montana: Geological Society of America Bulletin, v. 6, p. 389-422.

Weed., W. H., and Pirsson, L. V., 1896a, The Bearpaw Mountains, Montana: American Journal of Science, 4th Series, n. 1, art. XXXIV, p. 283-301, art. XLI, p. 351-362.

Weed, W. H., and Pirsson, L. V., 1896b, The Bearpaw Mountains, Montana: American Journal of Science, 4th Series, n. 2, art. XVI, p. 136-148, art. XXIV, p. 188-199.

Woods, M. J., 1974, Textural and geochemical features of the Highwood Mountain volcanics, central Montana: Missoula, University of Montana, Ph. D. Dissertations, 121 p.

14

Minerals from Northwest Type Localities

Don Howard

In the last issue, we completed the update survey of zeolite species. That, together with the entire text of Rudy‟s Zeolites of the World, is now in the process of being put into a form accessible on MINDAT. It is our intention to try to keep that update current, so information about additions of species or occurrences will be greatly appreciated. During the discussion at our Spring meeting, an interesting project was purposed: to document some of the stories that surround the minerals first found in Oregon and Washington. That too, of course, is an ongoing process, as new minerals are identified and characterized. To start the process, I have made a list of the minerals I am currently aware of that name an Oregon or Washington site as their type locality:

Oregon Washington

1. Boggsite 1. Calciohilairite 2. Cowlesite 2. Ferrierite-Na 3. Cavansite 3. Ferritungstite 4. Erionite-K 4. Okanoganite 5. Oregonite 5. Paulingite-K 6. Paulingite-Ca 6. Zektzerite 7. 8. Slawsonite 9. Tschernichite

There are in addition a number of minerals that might have been, or should have been, included in that list, but for one reason or another have been discredited or ascribed to a different “first” site. We begin in this issue with two stories of discredited species, and one of the trials and tribulations of trying to name new minerals.

THE MICROPROBE

Published twice a year by the NORTHWEST MICROMINERAL STUDY GROUP

Donald G. Howard, Editor 356 S. E. 44th Avenue Portland, Oregon 97215 e-mail: [email protected]

DUES: $15 per year per mailing address, payable for each calendar year at the Spring meeting or by mail to the Secretary-Treasurer:

Patrick “Kelly” Starnes 1276 SE Goodnight Ave. Corvallis, OR 97333 e-mail: [email protected] 15

AWARUITE Ni3Fe (formerly Josephinite)

by Rudy Tschernich

Awaruite was named in 1885 by Skey from the type locality in the Gorge River, South Island New Zealand. It is a metallic white natural nickel-iron alloy found in nickel-chrome deposits in serpentinized peridotite metamorphic rocks. In Oregon it was given the local name josephinite.

Tiny grains of awaruite are found all over the world: in Australia, Austria, Canada, China, France, Italy, Jamaica, Morocco, New Zealand, Norway, Pakistan, Russia, Slovakia, Sweden, Switzerland, and the USA (MinDat).

Awaruite is also found in meteorites: Kaba meteorite found in Hungary, Dhofar 925 Lunar meteorite from Oman, Ningqiang meteorite in China, and on the Moon at the Apollo 14 Base (Fra Mauro) in basalt sample 14053 (MinDat).

Small grains of native nickel, iron, and cobalt are commonly associated with awaruite (Ni3Fe), wairuite (CoFe), pentlandite ((Fe,Ni)9S8), pyrrhotite (Fe1-xS), magnetite (Fe3O4), native copper, heazlewoodite (Ni3S2), unnamed nickel arsenide (Ni 5-x As3), andradite garnet (Ca3Fe2Si3O12), and serpentine ((Mg3Si2O5(OH)4) in the Josephine peridotite of northwest California and southwest Oregon (Leavell, 1983). This mineral assemblage is called josephinite. Large nickel-iron bearing nuggets, up to 3 cm in diameter, are found in creeks crossing the Josephine peridotite in Josephine Creek, Josephine County, Oregon and the Smith River in Northern California. These nuggets were found by early placer gold miners but were of no economic importance. The nuggets have long been a mineral curiosity and make the best specimens known for this mineral.. The nuggets typically are angular to rounded and are composed of awaruite and lamellar intergrowths of andradite.

Many origins have been given to the Oregon “josephinite”. Some people have proposed they are fragments of the earth‟s core or are meteorites. A more plausible hypothesis explains that the small grains in the rock have been formed from alteration of the peridotite to serpentine along fault zones by hydrothermal alteration, along with desulfurization and remobilization of the Fe- Ni sulfides (Leavell, 1983).

References:

1. Leavell, D.N.(1983) The Geology of Josephinite in the Josephine Peridotite, Southwest Oregon. PhD Dissertation, U of Mass. 2. MinDat.com 16

. FALCONDOITE (Ni, Mg)4Si6O15(OH)2 6H2O (locally named garnierite) by Rudy Tschernich

Falcondoite was approved as a new mineral species by IMA in 1976. It was described by Springer (1976) from the type locality at Loma Peguera, Bonao, Monsenor Nouel Province, Dominican Republic where it occurs as veins cutting a laterite. It was named for the contraction of FALCONbridge DOminica C. Por A., the mining company at the type locality.

Falcondoite forms green, yellowish green, and whitish-green, soft, resinous masses. It is the nickel analogue of sepiolite.

Garnierite is considered in part a synonym of falcondoite. Garnierite is a name given by Jules Garnier in 1864 to a green nickel “ore” found in pockets and fissures of weathered serpentinite, dunite, and peridotite in New Caledonia. Garnierite consists of a “mixture” of Mg-rich serpentine, talc, chlorite, and smectite that may contain up to 20 to 40% nickel. The “ore” is a mixture of minerals, therefore, garnierite is not considered a species.

Some pure lime green masses of the garnierite “ore” in the nickel laterite deposits at Riddle, Douglas County, Oregon are considered the mineral falcondoite. Garnierite “ore” is found at many localities in the world including several in Josephine County, Douglas County, and Curry County, Oregon and Washington (MinDat). True falcondoite is much less widespread and probably has not been differentiated from garnierite “ore” at most of the localities since it does not form terminated crystals.

References:

1. Springer, G.(1976) Falcondoite, nickel analogue of sepiolite. The Canadian Mineralogist, V 14, pp 407- 409. 2. MinDat.com

17

The story behind the naming of Cavansite

by Rudy Tschernich

In the summer of 1963 John Cowles found a blue, radiating, bladed mineral with heulandite in a highly altered red scoria type of basalt in a shallow pit along the Neer City Road, ½ mile from the intersection with highway 30, north of Goble, Columbia County, Oregon. In the fall of 1963, John sent samples of this blue unknown mineral to Dr. Lloyd Staples at the University of Oregon in Eugene for identification. After x-ray diffraction work, Dr Staples determined the blue material to be a new mineral and proceeded to characterize the mineral from the samples John had supplied. John called this very shallow pit the Charles W. Chapman quarry, although it was hardly a quarry. I visited the site once with John and by then it was weathered to soil and overgrown with blackberry vines. The site has produced no more than a couple of truckloads of weathered rock. Today, I cannot find a trace of the pit, but back in the 1960‟s John was able to collect about fifty small samples of this blue mineral and sent most of it to Lloyd Staples for study. All of the original x-ray work, chemical analysis, optical, and other tests done were from John Cowles‟s samples. It was John‟s understanding that the new mineral would be named “cowlesite” after him. None of the blue mineral samples contained terminated crystals. The best were just halves of radiating blue bladed aggregates, up to 5 mm in diameter, with only one group per specimen. By the time the testing had been done there were no more than a dozen specimens remaining.

Dr. Staples, filled out the International Mineralogical Association (IMA) form listing all the physical, chemical, and x-ray information for the possible new mineral and sent it to IMA. They then sent copies of the data and the proposed name for the mineral “cowlesite” to the 50 voting IMA member throughout the world for review and a vote. During this process, the voting member for the USA, which was at the Smithsonian, noticed that the blue mineral was the same as a mineral sent to them in the spring of 1961 by Mr. and Mrs. Leslie Perrigo of Fruitland, Idaho, who in the fall of 1960 had first noticed the blue mineral coating a rock face in a new roadcut near Owyhee Dam, Malheur County, Oregon. Together with Mr. and Mrs. Frank Zimmerman of Payette, Idaho, they sent samples of the blue mineral to Paul Desautels at the Smithsonian who reported that it was probably a new mineral., but no additional work was done on it. The blue mineral just sat there. They had dropped the ball. If this inaction had occurred anywhere else where the voting member of IMA was not aware of the other site, the new mineral would have been approved by IMA and the blue material would have been named cowlesite after John Cowles. The second unstudied locality for the new mineral was made known to IMA and they requested that both localities be studied and 18 the application for a new species be modified to include that data. A problem was then created in naming the mineral. Too many people wanted it named after themselves. The Perrigo‟s who found it first wanted it named after them. There are lots of possible new minerals that never get named after the person that first found it if the research is not completed and sent to IMA. All the original work had been done on the specimens found by John Cowles and the original proposed name was cowlesite. In order to solve the problem of naming, it was not named after any person. It was named after its chemical composition Ca (calcium), (Va) vanadium, and Si (Silica) ca- van-si-te. John Cowles felt he had been gypped.

By this time two mineralogists from the U.S. Geological Survey at Washington D.C. were added as authors of the new mineral. Howard T. Evans, Jr. a specialist on silicate structures, and James R. Lindsay. The first paper on cavansite was a short abstract (Staples and others, 1967). The main paper describing cavansite and pentagonite (another new species found during the study of material from the Owyhee Dam site) was then published (Staples and others, 1973).

Since then cavansite has been found in abundance in India. Traces of tiny terminated cavansite has been found in Brazil, New Zealand, and at Jaquish road south of Goble by (Wieting, 1995). Cavansite has never been found at the main collecting areas along Neer Road, Goble. Most of the blue material in that area is alterations of copper.

Since I knew this story about cavansite, when I found a new zeolite at Goble, I proposed that it be named cowlesite after John Cowles to make up for the fiasco with cavansite.

References:

1. Staples, L.W., Evans, H.T., and Lindsay J.R. (1967) Cavansite, a New Calcium Vanadium . Geo. Soc. of Am.Special Paper Abstract pp 211-212. 2. Staples, L.W., Evans, H.T., and Lindsay J.R. (1973) Cavansite and Pentagonite, New Dimorphous Calcium Vanadium Silicate Minerals from Oregon. Am. Min. V 58, pp 405-411. 3. Wieting, E.B. (1995) Cavansite from the Jaquish Road Cut, Goble, Columbia County, Oregon. Micro Probe, V8, No 1, pp14-16.