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Wyoming State Mineral & Gem Society, Inc. JadeAward StateWinning WSMGS Website: wsmgs.orgNews Volume 2019, Issue 2 Wyoming Agates WHAT ARE AGATES Chalcedony (cryptocrystalline quartz), in its pure form, is transparent when exposed to concen- trated light. When a small amount of impurities or foreign materials are added, the color of the cryptocrystalline quartz changes and its ability to transmit light decreases, creating semitransparent to translucent varieties of chalcedony. Agates are a form of chalcedony that contain pat- WSMGS OFFICERS terns caused by impurities within this cryptocrys- President: Jim Gray talline quartz. The most common agate patterns [email protected] caused by impurities are in the form of bands, concentric lines (dendritic), mottled, moss shaped Vice President: Linda Richendifer or plume-like. In addition, these patterns are often [email protected] different in color than the chalcedony that contains it. The book Agates by Karen A. Brzys lists that Secretary: Leane Gray over 16 different agate patterns can be found in [email protected] Wyoming. Treasurer: Stan Strike HOW DO AGATES FORM [email protected] Agates usually form in areas where surface water seeps through igneous rocks or volcanic ash. Historian: Rod Baltes continued on page 2 [email protected] Jade State News Editor: Jennifer Flowers Wyoming Agates Pages ........1-6 [email protected] WSMGS Info & Updates Pages ......7-10 Rockhound of Year Nominations Page .......... 11 RMFMS State Director: Stan Strike Acrylic Rock Painting Pages ... 11, 12 [email protected] Old Bird Found in Wyoming Page ..........13 Geology of Guernsey State Park Pages ....14-17 WebMaster Tech: Marlene Sibley WY RMFMS St Director Pages ...17, 18 [email protected] Club Reports Page ......18-21 Show Flyers Page ......22-24 The WSMGS conducts meetings WSMGS Directory & Officers Page ...........25 quarterly and as special events require Page 2 Volume 2019, Issue #2 Jade State News Wyoming Agates continued from page 1 As water flows through the cavities and crevices patterns for jasper are limited- the most common of the igneous rock or volcanic ash, it dissolves being banded or striated. the silica from these parent materials. If the dis- solved silica in the water has a particularly high WHAT IS A JASP-AGATE? concentration, a silica gel can form within open- By definition a jasp-agate is a “jasper agate”. ings of the rocks below. Eventually, that gel can Under a strong light, an agate is translucent and a crystallize into microcrystalline quartz. jasper is opaque to light- since both are chal- As more time goes by, additional layers of the cedony, the amount of impurities must cause the gel form creating “younger” bands of micro- difference. Therefore a Jasp-Agate is a combina- crystalline quartz on the surfaces of the fractures tion of an agate and jasper. A jasp-agate can be and cavities. During this time, it is very easy for recognized by a pattern separation of translucent impurities to get mixed into the silica mixture. and opaque chalcedony. [A jaspilite is defined This is how the agates get their coloring, band- as a rock of alternating bands of red jasper and ing and other patterns. Agates can also form less iron oxides=banded iron. For simplification in frequently, inside openings between and within the following listing of the major agate types and sedimentary rock layers. locations in Wyoming, jaspilites were listed as Both igneous and sedimentary rocks, if Jasp-Agates.] exposed to weathering and erosion over a long period of time, results in the agates (being harder) WHAT ARE PSEUDOMORPH AGATES? becoming separated from their original depo- Pseudomorph Agate is created by a process sitional material. This is the reason why agates in which quartz that is dissolved in groundwater are often found in streams or downhill from the fills in and duplicates the original cell structure of original layers of igneous or sedimentary rocks in a pre-existing organic material (such as wood or which they formed. bone). By definition, “pseudo” means false and “morph” means body so pseudomorphs are false WHAT ARE JASPERS bodies. Jasper is an opaque variety of chalcedony. Not being true agates, Pseudomorph Agates Opaque means if you hold it up to a light source will not be in the following listing of the major neither light nor images will come through it. The agate types and locations in Wyoming. high amount of impurities in the jasper is what makes them opaque. Agates tend to be translucent because they contain less impurities and foreign materials than jasper, though both are forms of MAJOR WYOMING AGATES chalcedony. The following is an alphabetized list of the HOW DO JASPERS FORM major agate areas and their approximate locations Jaspers generally form in areas where there is in Wyoming. Because weathering, erosion, and fine, soft sediment or volcanic ash. Over time, the deposition are constant in Wyoming, these areas silica rich mixture begins to combine and “ce- will expose new finds year after year. However it ment” the sediment into a solid mass. The varying is the Rock Hound’s responsibility to study these sediment and ash and the chemical weathering of locations and their current land ownership before the impurities within the jasper plays an important going to the field in search of Wyoming agates. role in the beautiful colors of some jasper depos- ANGEL AGATE / MOONSTONES: Angel Ag- its. With this sedimentary process, the resulting ates and moonstones are found in the Granite 1. 1 Jade1. State News Volume 2019, Issue #2 Page 3 Wyoming Agates continued from page 2 Mountains. [SWNW section 36, T29N, R89W]- north of Muddy Gap. Angel agate is a pale green- DRYHEAD AGATE: ish gray color with a chalky white surface coating. The Dryhead Agate, Moonstones are clear chalcedony shaped balls a colorful red and coated with opal and white ash and are typically white banded 1-3 inches in diameter. Both fluoresce a greenish- fortification agate, yellow with UV. These agates are located in a 6 weathers out of the inch zone in the upper sandstone sequence of the Phosphoria Formation split Rock formation. the northern Bighorn Basin [T58N,Rs94, 95W]. Some bands of this agate will fluoresce green un- BLACK BUTTES JASP-AGATE: This jasp-agate der short wave UV light. is described as reddish brown to dark gray with this veins of white quartz [NE section 26, T50N, FAIRBURN AGATE: R62W] Also at this location mineral ores can be In the Black Hills of found as a within a breccia resulting from min- northeastern Wyoming eralization occurring with silification within the agates and Jasp-Agates Pahasapa Limestone. can be found in the The mineral ores are contained in a breccia of glacial outwash and limestone cemented by massive galena which may stream gravels. The Fairburn Agate is rarely found also contain: hemimorphite (white prismatic crys- and is identified by its brilliant colors and “holly tals filling vugs of reddish brown jasper), wulfen- leaf” shaped fortification lines. The Teppee Can- ite (resinous, transparent yellow to yellow orange yon agate found in Custer County, South Dakota crystals), with minor occurrences of sphalerite can also be very colorful and have holly leaf (dark, resinous brown) fortification lines but have a limestone covering and fluorite (deep purple). whereas Fairburn Agates’ have a waxier micro- crystalline quartz based covering. BRIDGER AGATE: Bridger Agate is a dark gray to brown agate associated with the Bridger Forma- LYSITE AGATE: tion south of Crooks Mountain [T26N,Rs96 - 97W Today Lysite & NW part of T27N, R97W]. Agate is found in isolated pockets CEDAR MOUNTAIN AGATE/JASP-AGATE: of the Lysite Along the eastern flank of Cedar Mountain several Member of the varieties of chalcedony can be found [Sections White River Formation or as isolated pieces 2 &19,T14N,R110W//Sections 22,24,25,T14N, (“float”=separated by gravity) that have been R111W// Section 23,T15n, R111W]. The agates exposed by the continual weathering and erosion are multicolored to black with moss, flame, and of Lysite Mountain. [T40N,R90W) Lysite Agate plume patterns. The jasp-agate is red and yellow collected from the Lysite Mountain area is usu- with white and blue streaks. Zebra flint is also ally coated with a calcite layer, which requires found in this area and is white, brown, and black most finds to undergo some lapidary treatment striped flint. All of this material originates from the in order to create a “gemstone specimen”. Be- Bishop Conglomerate which caps Cedar Mountain cause the chemical conditions that created this on the west and south. agate changed, Lysite Agate exists in many dif- ferent forms. Lysite Agate most often appears as Page 4 Volume 2019, Issue #2 Jade State News Wyoming Agates a banded silica base agate with fortification lines 22, T17N, R104W] is a dark to light gray agate created by colors ranging from reds to browns and with cross-cutting veins of quartz, and banded white or clear (rare-blue) interlayered with calcite- red, yellow-orange, and gray jasp-agate. based material. Lysite Agate also can occur with larger crystals of quartz and calcite deposited in SEMINOE MOUNTAIN JASP-AGATE: This voids, or with cavities covered with small crystals jasp-agate is found in the stream gravels that are = Drusy Appearance, or with a surface covered washed down from the Seminoe Mountains near with small rounded/grape-like bumps = Botryoi- the Miracle Mile of the North Platte River. It dal Appearance. contains a mixture of jasperized iron that is mag- netic and appears as alternating layers of black MEDICINE BOW magnetite, dark gray quartz, and brown layers of PLUME AGATE: jasper and grunerite. Medicine Bow Plume Agate features dark plume SHIRLEY BASIN JASP-AGATE: In the north- inclusions set in ern Shirley Basin a jasp-agate can be found that milky white consists of pink breccia matrix cemented together translucent chalcedony.

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