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Appendix 1 Calculation of a Chemical Formula from a Mineral Analysis

Appendix 1 Calculation of a Chemical Formula from a Mineral Analysis

Appendix 1

Calculation of a chemical formula from a analysis

Appendix 1

Magnesiohornblende analysis

3 4 2 Atomic proportion No. of anions on 1 Molecular of from basis of 24 (O,OH) 5 Wt.% of oxides proportion of oxides each molecule i.e. col. 368.3735 No. of in formula

SiO 51.63 0.8594 1.7188 14.392 Si 7.196 2 8.00 0.804 } Al2O3 7.39 0.0725 0.2175 1.821 Al 1.214 0.410 3+ Fe2O3 2.50 0.0157 0.0471 0.394 Fe 0.263 FeO 5.30 0.0738 0.0738 0.618 Fe2+ 0.618 5.07 MnO 0.17 0.0024 0.0024 0.020 Mn 0.020 } MgO 18.09 0.4489 0.4489 3.759 Mg 3.759 CaO 12.32 0.2197 0.2197 1.840 Ca 1.840 2.00 Na2O 0.61 0.0098 0.0098 0.082 Na 0.164 } H2O+ 2.31 0.1282 0.1282 1.073 OH 2.146 2.15 Total 100.32 2.8662 24 = 8.3735 2.8662

The procedure for calculating a chemical formula is Column 5 gives the number of cations associated described by means of the above example, a with the in column 4. Thus for SiO2 there is magnesiohornblende. one for two oxygens so the column 4 entry is divided by 2. For A12O3 there are two aluminiums for Column 1 lists the composition of the mineral every three oxygens so the column 4 entry is multiplied expressed in the usual manner as weight percentages by ~˜. For divalent ions the column 5 value is the same ¯ of oxides. as that of column 4, and for monovalent ions (including ) the latter is doubled in column 5. Column 2 is derived by dividing each column 1 entry The numbers of ions on the basis of 24 oxygens by the molecular weight of the oxide concerned (see given in column 5 can be grouped as shown to conform Appendix 2). The figures so obtained therefore express to a structural formula. In the present example it is the molecular proportions of the various oxides. assumed that the tetrahedral sites which are not filled by Si are occupied by Al, and the remaining Al atoms are Column 3 is derived from column 2 by multiplying by in octahedral coordination. the number of oxygen atoms in the oxide concerned. It It should be noted that a chemical analysis in itself thus gives a set of numbers proportional to the numbers can give only the ratios of atoms in the formula, and of oxygen atoms associated with each of the elements that the actual numbers of atoms given depends on an concerned. At the foot of column 3 is its total (T). assumption about the actual number of one of them or If we require the formula based upon 24 of a group of them. A check of the correctness of the oxygen atoms (this represents half the content of the formula can be made if the cell volume and are unit cell) we need to re-cast the oxygen atom accurately known, since a calculated density can then be proportions so that they total 24. This is done by compared with that measured. multiplying all of them by 24/T and the results are A check of charge balance, made by adding positive given in Column 4. and negative charges in the formula, is a check only on

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arithmetic and not on the quality of the analysis. This is The procedure for obtaining column 2 is as before, because any analysis expressed in terms of neutral the fluorine content being divided by 19, the atomic oxides must lead to numbers of cations and oxygens weight of fluorine. For column 3 the number of fluorine which balance electrically. atoms is inserted along with the oxygens and the total is In many , as in the example above, the only again too high. It is necessary to subtract the oxygen anion in the mineral is oxygen (or OH). Each element is equivalent of the fluorine atoms, i.e. half their number, expressed (and generally directly determined) as a to give a true total. weight percentage of oxide, even though the oxides do In the case of fluorphlogopite, the number of anions not exist as such in the mineral. The calculation (O,OH,F) assumed is 24, so that the total of column 3 is procedure outlined is justifiable, as each element can divided into 24 to give the multiplying factor which is be thought of as associated with its appropriate share of applied to produce column 4. Column 5 is derived as the oxygen atoms in the structure. before. If oxygen is not the only anion present the Many modern analyses are carried out by use of an calculation is somewhat more complicated, and an electron microprobe and this method does not yield 2+ example (a fluorphlogopite) is shown below. values for H2O and does not differentiate between Fe Here fluorine is shown, as well as the oxides of all and Fe3+. the cations, as a weight percentage. We may assume for If H2O has not been determined or is thought to be simplicity that the fluorine atoms in the structure are unreliable the mineral formula can be calculated on an bonded to atoms only, and yet the same anhydrous basis assuming the (OH) content to be ideal. atoms of magnesium are recorded as combined with Thus for the magnesiohornblende example above, oxygen in MgO. Thus an excess of oxygen is recorded instead of using 24(O,OH) to derive the scaling factor, and the total will exceed 100%. To obtain a real total 23(O) equivalents [i.e. 22(O) + 2(OH)] can be assumed (which is a measure to some extent of the accuracy of as associated with all the cations apart from hydrogen. the data), an oxygen equivalent of the fluorine atoms If Fe3+ has not been determined, total is usually must be subtracted. presented as an FeO equivalent. There are many ways of One excess oxygen atom is recorded for each two gaining an estimate of Fe3+ and Fe2+,mostofwhichare atoms of fluorine present, so that the oxygen equivalent referred to by Droop (1987). The most appropriate of a fluorine by weight is obtained by multiplying the method depends upon the mineral concerned. Some fluorine content by the factor methods re-assign Fe to Fe2O3 and FeO in the way which gives the ideal total for all the cations or for atomic weight of oxygen 16 ; i.e. particular groups. Some adjust Fe so that trivalent ions 2 Â atomic weight of 38 in octahedral sites balance the Al replacing Si in tetrahedra. All methods depend on assumptions which The oxygen equivalent of the fluorine weight is may or may not be warranted and all may give only an subtracted from the total of column 1 to give a true total. approximate result.

Fluorphlogopite analysis

3 4 2 Atomic proportion No. of anions on 1 Molecular of oxygen from basis of 24 (O,OH) 5 Wt.% of oxides proportion of oxides each molecule i.e. col. (3)68.500 No. of ions in formula

SiO2 41.18 0.6854 1.3708 11.651 Si 5.826 Al2O3 12.52 0.1228 0.3684 3.131 Al 2.088 TiO2 0.99 0.0124 0.0248 0.211 Ti 0.105 FeO 0.30 0.0041 0.0041 0.034 Fe 0.034 MnO 0.04 0.0005 0.0005 0.004 Mn 0.004 MgO 27.32 0.6779 0.6779 5.762 Mg 5.762 Na2O 0.88 0.0142 0.0142 0.121 Na 0.241 K2O 11.93 0.1266 0.1266 1.076 K 2.152 H2O+ 1.06 0.0588 0.0588 0.500 OH 1.000 F 6.74 0.3547 0.3547 3.113 F 3.113 102.96 3.015 –O:F 2.84 À0.1773 = 760.3547 Total 100.12 2.8235 24 = 8.500 2.8235

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Further reading

Droop, G.T.R. (1987) A general equation for estimating Fe3+ concentrations in ferromagnesian silicates and oxides from microprobe analyses using stoichiometric criteria. Mineralogical Magazine, 51, 431À435.

Appendix 2

Appendix 2

Atomic and molecular weights for use in calculations of mineral formulae from chemical analyses.

Al2O3 101.96 H2O 18.015 S 32.06 B 10.81 HfO2 210.49 SO3 80.06 B2O3 69.62 K2O 94.20 Sc2O3 137.91 BaO 153.33 La2O3 325.81 SiO2 60.08 BeO 25.01 Li2O 29.88 SnO 134.71 CO2 44.01 MgO 40.30 SrO 103.62 CaO 56.08 MnO 70.94 Ta2O5 441.89 CeO2 172.12 MnO2 86.94 ThO2 264.04 Ce2O3 328.24 Mn3O4 228.81 TiO2 79.87 Cl 35.45 Na2O 61.98 UO2 270.03 CoO 74.93 NiO 74.69 U3O8 842.08 Cr2O3 151.99 Nb2O5 265.81 V2O5 181.88 CuO 79.55 P2O5 141.94 Y2O3 225.81 F 19.00 PbO 223.20 ZnO 81.38 FeO 71.84 Rb2O 186.94 ZrO2 123.22 Fe2O3 159.69

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End-member calculations

Appendix 3

For some purposes it can be useful to express the and Fe2SiO4(Fa) may suffice, but the Mn2SiO4 ( formula of a mineral which can show a range of end-member) could also be calculated. If the Mn content compositions between specified end-members, in terms is low it is usually included with Fe as part of the Fa of the percentages of these end-members. There is no component. For a minor constituent the decision needs single procedure for the required calculation as different to be taken as to whether to ignore it or include it as assumptions are needed for different and proxying for a major element, and if so, for which different purposes. In general a relatively small element. number of ‘major’ constituent end-members are The examples given below help to indicate the kinds specified. In the , for example, Mg2SiO4(Fo) of procedures adopted.

Olivine

Ideal formula (Mg,Fe)2SiO4. End-members: Mg2SiO4(Fo)ÀFe2SiO4(Fa). Example formula on basis of 4(O): 3+ 2+ (Si0.97Al0.03)1.00(Ti0.02Fe0.01Mg1.91Fe0.04Mn0.01)1.99 End-member percentages: 100Mg/(Mg + Fe*) = 191/1.96 = 97.4% 2+ 3+ (where Fe* = Fe +Fe ) } Fo97.4Fa2.6 100Fe*/(Mg + Fe*) = 5/1.96 = 2.6% 2+ 3+ If Fe* = Fe +Fe + Mn. Fo = 191/1.97 = 96.9%: Fo96.9Fa3.1

Augite

Ideal formula (Ca,Mg,Fe)2(Si,Al)2O6. End-members: Mg2Si2O6(En)ÀFe2Si2O6(Fs)ÀCa2Si2O6(Wo). Example formula on basis of 6(O): 3+ 2+ (Si1.94Al0.06)2.00(Al0.01Fe0.03Ti0.02Mg0.21Fe0.87Mn0.02Ca0.82Na0.02)2.00 End-member percentages: 100Mg/(Mg + Fe* + Ca) = 21/1.95 = 10.77% 100Fe*/(Mg + Fe* + Ca) = 92/1.95 = 47.18% 100Ca/(Mg + Fe* + Ca) = 82/1.95 = 42.05% 2+ 3+ (where Fe* = Fe +Fe +Mn);i.e.En10.77Fs47.18Wo42.05 3+ Alternative including end-member NaFe Si2O6(Ac) 100Na/(Mg + Fe* + Ca + Na) = 2/1.97 = 1.02%

leaving 21/1.97(En), 92/1.97(Fs) and 82/1.97(Wo), i.e. En10.66Fs46.70Wo41.62Ac1.02

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Garnet

2+ 3+ Ideal formula (Mg,Fe ,Mn,Ca)3(Al,Fe ,Cr)2(Si,Al)3O12. 2+ End-members: Mg3Al2 ; Fe3 Al2 almandine; Mn3Al2 ; 3+ Ca3Al2 ; Ca3Fe2 ; Ca3Cr2 Example formula on basis of 24(O): 3+ 2+ (Si5.98Al0.02)6.00(Al3.91Fe0.13Cr0.03)4.07(Mg3.58Fe1.55Mn0.04Ca0.73)5.90

End-member percentages pyrope 358/5.90 = 60.68%, andradite 13/4.07 = 3.19% almandine 155/5.90 = 26.27%, uvarovite 3/4.07 = 0.74% spessartine 4/5.90 = 0.67%, S(and + uv) 16/4.07 = 3.93%

gro + and + uv = 73/5.90 = 12.37% gro = 12.37 À S(and + uv) = 12.37 À 3.93 = 8.44%

Result: py60.7alm26.3gro8.4and3.2uv0.7sp0.7

Feldspar

Plagioclase : as for but use 100Ca/(Ca + Na) = An 100Na/(Ca + Na) = Ab Alkali feldspar: as for olivine but use

100Na/(Na + K) = Ab 100K/(Na + K) = Or Ternary feldspar: as for but use 100Ca/(Ca + Na + K) = An 100Na/(Ca + Na + K) = Ab 100K/(Ca + Na + K) = Or

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Use of optical identification tables

Appendix 4

The (d) exhibited by a crystal varies with should be readily narrowed by observation of other orientation, but the maximum birefringence shown by properties using Table B as suggested below. of a mineral (of specific composition) in a range Also at a fairly basic level of investigation would be of orientations is characteristic of that mineral. some (mostly qualitative) observations in plane polarized ‘Maximum birefringence’ might also, however, be light, including prominent (s), and taken to mean the highest characteristic value shown ‘relief’ (high, moderate or low). A further level would by the members of a chemical series, e.g. involve observing interference figures in convergent (Mg2SiO4)– (Fe2SiO4). Use of birefringence light to determine whether a mineral is uniaxial or diagnostically needs to take account of both meanings, biaxial, and using a testing instrument, to determine the former to determine a meaningful value, and the optic sign. The above properties are listed in that order latter to allow for the possible ‘chemical range’ when in Table B. For each mineral treated in the present text, using that value to suggest a mineral name. this Table gives the range of d that results from The petrological use of the polarising microscope can chemical variation, and the minerals are listed in be treated at different levels according to the needs of numerical order according to the low birefringence end different student groups. At one level would be the of that range. practical observation of the colours of a mineral in thin For more detail and for quantitative data such as section between crossed polars and relating these to optical orientation, extinction angles and values of the birefringence (d)a. This relationship is presented here in optic axial angle (2V), Table B gives the starting page Table A for use with a of standard reference for each mineral. More general properties thickness, 0.03 mm. (The presence of twinning is also (colour, hardness, density, etc.) are also listed there. In best observed between crossed polars, and isotropic addition, the text for each main mineral contains a minerals could be noted). In Table A alongside each d section headed ‘Distinguishing features’ which helps value are the minerals that possibly match but, mainly discriminate between that mineral and a selection of because of chemical variation, those somewhat lower in others with which it might be confused. the chart need also to be considered. The possibilities

a Similar colours in different ‘orders’ can be distinguished by gradually inserting a wedge testing instrument to ‘compensate’ those colours , and observing the gradual changes of colours as the net birefringence is reduced to zero.

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Table A. and Michel-Le´vy interference colours (0.03 mm thin section) for the most common rock-forming minerals (colour strip (calculated) kindly provided by Professor Takenori Kato, Nagoya University, Japan (http://www.nendai.nagoya-u.ac.jp/gsd/sicc/).

0.000 *chlorite (mid-range) erionite, (some), stilbite chabazite apatite, , , vishnevite *clinozoisite, (marialite) 0.005 , chamosite, -, kalsilite, , antigorite, *, , lizardite, *, , K-feldspar akermanite, corundum, , celestine, , clinozoisite, quartz, stilbite, topaz 0.010 chlorite (Mg-rich), , , (Na-rich) andalusite, arfvedsonite, , gehlenite, staurolite First order First , , anthophyllite, , plagioclase (Ca-rich) *, enstatite-ferrosilite, (mid-range) 0.015 , (mg-rich), , () riebeckite, boehmite, *chlorite (Fe-rich) augite (Mg-rich), ferroactinolite, ferrosilite, , 0.020 , gibbsite, , , lawsonite , tourmaline (dravite), ferrosilite,

augite (mid-range), hedenbergite 0.025 order ferro-richterite, gedrite

Second 0.030 -augite, glauconite (Fe-rich), , , , stilpnomelane cummingtonite-grunerite (mid-range), * ferro-augite scapolite () 0.035 olivine (forsterite),

Isotropic (n) 0.040 aegirine-augite, , diaspore 1.433 p. 480 1.474 – 1.493 p. 363 1.483 – 1.490 p. 340 1.508 – 1.511 leucite p. 334 1.544 halite p. 483 1.710 – 1.890 p. 18 0.045 grunerite, monazite 1.735 periclase p. 382 1.719 MgAl p. 407 1.835 – 2.740 p. 402

Third order Third 2.260 – 2.400 p. 400

High birefringence (δ) 0.050 aegirine, , pyrophyllite, 0.096 – 0.098 p. 383 0.172 – 0.190 p. 453 olivine (fayalite) 0.179 – 0.185 p. 463 0.190 – 0.218 p. 459 0.207 – 0.242 siderite p. 461 * can show anomalous interference colours

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Table B. Optical properties of common minerals in order of increasing birefringence.

Relief: L low, M moderate, H high, VH very high; all with R.I >1.54 (standard mounting medium). LÀ,MÀ, negative relief. (R.I. <1.54). Cleavage: * one cleavage commonly visible. ** two intersecting cleavages. Pleochroic: * can show pleochroism. U: uniaxial, B: biaxial, +: positive, À: negative, (+ À): either positive or negative.

Birefringence Relief Cleavage Pleochroic U B + À (+ À) Page 0.00À0.01 chlorite (mid-range) M * * * * 208 0.001À0.005 chabazite MÀ * * 374 0.001À0.007 apatite M ** * 473 0.001À0.009 vesuvianite H * * 28 0.001À0.013 melilite M*** * 72 0.002À0.004 vishnevite LÀ * * * 345 0.002À0.004 a-tridymite MÀ ** 311 0.005À0.020 approx. cancrinite LÀ * * * 345 0.003 a cristobalite MÀ * * 311 0.003À0.004 clinoptilolite MÀ * * * 372 0.003À0.005 erionite MÀ * * 355 0.003À0.005 LÀ * * 325 0.003À0.008 zoisite H* ** 53 0.003À0.009 heulandite MÀ * * * 372 0.003À0.010 phillipsite MÀ ** 368 0.004À0.005 mordenite MÀ * ** * 377 0.004À0.005 scapolite (marialite) L ** * * 349 0.004À0.007 antigorite L* * * 216 0.004À0.009 beryl L * * 76 0.004À0.015 clinozoisite H* ** 56 0.005À0.006 kalsilite LÀ * * 325 0.005À0.008 harmotome MÀ ** 368 0.005À0.010 LÀ ** * * 291 0.005À0.022 chloritoid H** * * 47 0.006À0.008 lizardite L* * * 216 0.006À0.010 K-sparÀNa-spar LÀ ** * * 253 0.006À0.016 riebeckite H ** * * * 162 0.006À0.021 jadeite H ** * ** 125 0.006 approx. kaolinite L* * * 227 0.007À0.021 katophorite H ** * * * 167 0.007À0.016 enstatite H ** * * * 102 0.008 approx. LÀ ** * * 253 0.008À0.009 corundum H ** * 384 0.008À0.011 topaz M** ** 44 0.008À0.018 cordierite L** * * 80 0.008 approx. a˚kermanite M * * 72 0.009 a-quartz L * * 311 0.009À0.010 stilbite LÀ * * * 335 0.009À0.012 andalusite M* * * 33 0.009À0.013 celsian M ** ** 291 0.009 approx. celestine M ** * ** 444 0.01À0.04 smectite L* * * 234 0.010À0.012 arfvedsonite H ** * * * 169 0.010À0.012 laumontite LÀ ** * * 370 0.010À0.020 pumpellyite H ** * * * 68 0.010 approx. LÀ ** ** 253 0.010 approx. gypsum LÀ * ** 445 0.011À0.014 staurolite H** ** 39 0.011 approx. gehlenite H * 72 0.012À0.016 kyanite H** * * 36 0.012 approx. natrolite MÀ * ** 366 0.012 approx. baryte M ** ** 441 0.013À0.014 wollastonite M ** * * 132 0.013À0.017 chrysotile L 216 0.013À0.020 eckermannite H ** * * * 169

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Table B (contd.)

Birefringence Relief Cleavage Pleochroic U B + À (+ À) Page 0.013À0.021 anthophyllite M ** * * 144 0.013À0.036 allanite H * * * 63 0.013 approx. L ** * * 292 0.014À0.020 brucite M * * * 409 0.014À0.027 H ** * * 131 0.012À0.028 omphacite H ** * * * 122 0.015À0.020 boehmite M * * 414 0.015À0.022 kosmochlore H ** * * * 125 0.015À0.022 Mg-richterite H ** * * * 167 0.015À0.051 epidote H * * * * 56 0.016À0.022 ferrosilite H ** * * * 102 0.017À0.021 tourmaline (elbaite) M * * * 86 0.018À0.022 sillimanite H * * * * 30 0.018À0.025 augite H ** * * * 116 0.018À0.035 lepidolite L * * * * 195 0.019À0.021 lawsonite H ** * * 65 0.02À0.03 glauconite M * * * 188 0.02À0.03 vermiculite L * * * * 239 0.02 approx gibbsite L * * * 410 0.02 approx hornblende H ** * * * 154 0.020À0.032 cummingtonite H ** * * 147 0.021À0.029 gedrite H ** * * * 144 0.021À0.029 tourmaline (dravite) M * * * 86 0.022À0.017 ferro-actinolite H ** * * * 150 0.022À0.029 johannsenite H ** * * 112 0.022À0.029 Fe-richterite H ** * * * 167 0.022À0.051 prehnite M * * * 244 0.023À0.020 glaucophane M ** * * * 162 0.023À0.029 pigeonite H ** * * * 109 0.025À0.073 H * * * * 61 0.025À0.033 ferro-augite H ** * * 116 0.025À0.035 tourmaline (schorl) H * * * 86 0.027À0.022 tremolite M ** * * 150 0.028À0.024 hedenbergite H ** * * * 112 0.028À0.047 kaersutite H ** * * * 160 0.028À0.07 phlogopite-biotite M * * * * 189 0.03 À0.11 stilpnomelane H** * * 199 0.03 approx. illite L* * * 230 0.030À0.045 aegirine-augite H ** * * * 128 0.034À0.028 diopside H ** ** 112 0.032À0.045 grunerite H ** * * * 147 0.024À0.034 scapolite (meionite) L * * 349 0.035 forsterite H ** 5 0.035 approx. zinnwaldite L** * * 198 0.035À0.042 muscovite M* * * 181 0.04À0.05 diaspore H* ** 412 0.04 approx. anhydrite L ** ** 448 0.040À0.060 aegerine H ** * * * 128 0.042À0.065 zircon H * * 12 0.045À0.075 monazite H* * * 478 0.050 approx. pyrophyllite M* * * 202 0.050 approx. talc M* * * 204 0.052 olivine (fayalite) H * * * 5 0.073 approx. H ** * * 396 0.096À0.098 cassiterite H * * 383 0.100À0.192 H** ** 15 0.117À0.158 H ** 398 0.138À0.140 H** * * 418

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Table B (contd.)

Birefringence Relief Cleavage Pleochroic U B + À (+ À) Page 0.149À0.150 { L,H * * * 471 0.155À0.156 { L,H * * * 468 0.172À0.190 calcite{ L,H * * * 453 0.179À0.185 dolomite{ L,H * * * 463 0.182À0.202 { L,H * * * 456 0.190À0.218 magnesite{ L,H * * * 459 0.207À0.242 siderite H* * * 461 0.28 approx. VH * * 387 0.286À0.296 VH * * * 393 0.57 approx. lepidocrocite H** * * 420 { Relief changes markedly on rotating polariser

Isotropic minerals (n) 1.433 fluorite HÀ * 480 1.479À1.493 analcime MÀ 363 1,483À1.490 sodalite MÀ 340 1.508À1.511 leucite LÀ 334 1.544 halite L * 483 1.71À1.89 garnets H 18 1.735 periclase H * 382 1.719À2.74 spinels H 402 2.30À2.38 perovskite H 400

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Index

Mineral names in bold type are those described in detail; page numbers in bold type refer to the principal descriptions or definition of the mineral. Entries other than mineral names are in italic type, t refers to a table.

Acmite 128 Aragonite 451, 454t, 468–70 Cancrinite 347 Actinolite 140t Arfvedsonite 142t, 169–71 Cancrinite–Vishnevite 345–8 Adularia 250, 282, 288 Arsenopyrite 424 451–72 Aegirine-augite 128–30 Asbestiform 145, 149, 151, 164 Carlsbad twins 265–6, 298 Aegirine 99t, 128–30 Asbestos 164–5, 216, 221 Carnegieite 325 133 Asterism 192 Cassiterite 383 318 Augite–Ferro-augite 98t, 116–21 Cation exchange 224, 231, 236, 240 Akagane´ite 417 Authigenic albite 309 Cattierite 424 A˚ kermanite 72–5 Aventurescence 352 Ce-perovskite 400 Al hydroxides and oxyhydroxides Aventurine feldspar 280, 306 Cebollite 74 409–15 Azurite 452 Celadonite 177, 188 Alabaster 447 Celestine 441, 444 Alamosite 133 Baddeleyite 394 Celsian 291 Albite 248, 253, 256, 258–9, 261, 264, Baileychlore 210, 211 Cerussite 440, 452 268, 272, 292, 299t, 309 Barium 291 Chabazite series 355, 356–7, 374–6 Albite: authigenic 309 Barroisite 139, 167 312, 318 Albite: twins 265–7, 304–5 Baryte 441–3 Chalcocite 433 Alexandrite 385 ‘Basic’ sodalite 341 Chalcopyrite 432–4 Alkali Feldspar 248–90 Bassanite 446 Chalcopyrite disease 433 analyses 270 Bastite 106 Chamosite 208–15, 211t, 222 electron microscopy 280–2 411, 414 Cheralite 478 order–disorder 272 Baveno twins 265–7 318 relationships in magmas 283 Bayerite 329 Chiastolite 34 solvus curves 274–6 ‘Beef’ (calcite) 457 China 229 system Ab–Or–Q–H2O273Behaviour diagrams 258–60, 275 Chlorapatite 473, 475 Allanite 58t, 63–4 Beidellite 225, 235, 237 Chlorite 211t Almandine 18, 20, 22 Berthierine 210, 216, 222 208–15 Altaite 439 Beryl 76–9, 78t Chloritoid 47–51 Aluminotschermakite 141t Biotite 177t, 179t, 189–94 Chlorophaeite 8 196 Biotite-vermiculite 183 Chondrodite 4, 9 Amesite 210, 216, 222 Blue John fluorite 481, 482 Chrome-pyrope 19, 25–6 317 Boehmite 414–5,420 402, 406, 408 Amosite 149 Bøggild intergrowths 249, 294–5, Chromite series 406 Amphibole structure 137 306, 308 Chrysoberyl 77 Amphibole Group 137–71 Bowlingite 8 Chrysotile 7, 216–21t Analcime 355, 357, 363–5,364t Braid perthite 263, 279–81, 288 Citrine 317 Anatase 396–7 Brammallite 187, 231 Clausthalite 439 Andalusite 33–35,37t Bravoite 424 Clay Minerals 224–43 Andesine 250, 393 Brazilian‘’ 45 Cleavelandite habit 298 Andradite 18, 20 Breunnerite 459 Clinochlore 208–15,211t, Anglesite 440–1 357 Clinochrysotile 216, 220 Anhydrite 448–9 Brewsterlinite 45 Clinoenstatite 102–3 Ankerite 451, 452, 454t, 463 Brookite 398–9 Clinoferrosilite 103 Annite 179t, 180t, 189–94 Brucite 409 4, 10 Anorthite 292–4 270 Clinoptilolite-K 372 Anorthoclase 268–9, 277–8, 282, 287 Buergerite 88–9 Clinoptilolite series 355, 372–3 Anorthosite 307 Bustamite 132 Clinozoisite–epidote 56–60 Anthophyllite 139t, 144–6 Bytownite 250, 393 Clintonite 177 Antigorite 216, 219, 220, 221t 312, 315, 322 Antiperthite 260, 297 Calciocelsian 291 Coherent/incoherent intergrowth 260 Antozonite 480 Calcite 451, 453–8, 454t Collophane 475 Apatite 473–7,475t 21 Convergent/non-convergent ordering Aquamarine 78–9 Californite 28 257, 261

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Cookeite 210 Feldspathoids 325–54 95 Cordierite 80–5,81t Fe oxyhydroxides 417–21 Grossular 18, 20 Corrensite 210 Feroxyhyte 417 Grothite 16 Corundum 384–6,385t Ferrierite 357 Groutite 418 Cristobalite 311, 313–5, 317, 319, 321 Ferrihydrite 417, 421 Grunerite 140t, 147–9 Crocidolite 164–5 Ferripyrophyllite 202 Gypsum 445–7 Cronstedtite 210, 216 Ferristilpnomelane 199–201 Cryolite 481 Ferro-actinolite 140t, 150–3 Cryptoperthite 249, 263 Ferroan talc 205 Hackmanite 341, 342, 343 Crystallinity index 231 Ferro-augite 98t, 116–21 13 Cummingtonite–Grunerite 140t, 147–9 Ferrobrucite 409 Halides 480–4 Cyprine 28 Ferrobustamite 113, 117, 132 Halite 483–4 Ferro-edenite 154–9 -10A˚ 227 Ferroglaucophane 142t, 163 Halloysite-7A˚ 227 Dachiardite 357 Ferrohornblende 154–9 Halloysite 225–6, 229 Dahlite 474 Ferrohortonolite 7 Hancockite 57 Dannemorite 148 Ferrokaersutite 160–1 Harmotome 355–7 Datolite 245 Ferropargasite 154–9 Hastingsite 141t, 154 Demantoid 22, 26 Ferropericlase 382 424 Desert rose 442, 447 Ferrorichterite 167–8 Hau¨yne 340–4, 342t Diaspore 412–3 Ferrosaponite 236 Hectorite 235, 237 227–8 Ferrosilite 98t, 100, 102–8 Hedenbergite 98t, 112–5 Differential thermal analysis Ferrostilpnomelane 199–201 Heliodor 78 202, 211, 220, 228, 231, 236, 241 Ferrotschermakite 154–9 Helvite 79 Digenite 433 Fibrolite 30 Hematite 387–9 Dioctahedral chlorite 210 Film perthite 279–81 Hepatite 441 Diopside–Hedenbergite 98t, 112–5 318 Hercynite 402–5, 407 Distribution coefficient Fluid inclusion 281, 318 Hessonite 22 biotite/ 192 Fluor-dravite 86 Heulandite-Ca 372 104 Fluor-elbaite 86 Heulandite series 355–7, 372–3 Dolomite 451, 454t, 463–7 Fluor-olenite 86 Hexagonal pyrrhotite 429 Donbassite 213, 215 Fluor-schorl 86 HF etching (feldspars) 280 Donpeacorite 95, 103 Fluor-uvite 86 Hibschite 18, 21 Dravite 86–92,90t Fluorapatite 473, 475 Hiddenite 131 Fluorite 480–2 High albite 253–4 Eastonite 189–94 Foitite 88 High 253–4, 278 Eckermannite 139, 142, 169 Forsterite 8 Holmquistite 146 Eckermannite–Arfvedsonite 169–71 Framboidal texture () 426 Hornblende 140t, 154–9 Edenite-Ferro-edenite 139t, 154–5 Francolite 474, 475 Hortonolite 7, 8 366 Franklinite 402, 405, 408 Hour-glass structure 221, 244 Elbaite 86–92,90t Fuchsite 182 Hourglass zoning 129 Emerald 77–9 Fuller’s earth 236–7 4, 10 Enantiomorphism 317 Humite Group 4 Enstatite–Ferrosilite 102–8,98t Huntite 451, 452 Epidote Group 52–64 Gahnite 402, 404, 407 Hu¨ttenlocher intergrowths 249, 294–6, Epidote 56–60,58t 402, 404 306, 308 Epistilbite 357 Galena 439-40 478 Erionite 355, 357–8, 374 Garnet Group 18–27 Hyacinth 13 Esseneite 95 Gedrite 139t, 144–6 Hyalophane 291 131 Gehlenite 72–5, 73t Hyalosiderite 7 Europium anomaly 298 391 Hydroandradite 21 Exfoliation 239–40 Geothermometry 24, 104 Hydrogarnet 19, 21 Extinction angle (plagioclase) 304–6 Gibbsite 410–1 Hydrogrossular 18, 22 Gismondine 355, 357 Hydromuscovite 183 Faujasite 357 Glauconite 188,231 Hydrosodalite 340 Fayalite 8–11 Glaucophane 139t, 141t, 162–6 Hydroxyl-fluorapatite 475 Fe-Mg distribution coefficient 24 Glycerol 235, 239, 241 Hydroxylapatite 473, 475 Feldspar twin laws 265 Glycol 226, 228, 230, 239 Feldspar Group 248–309 Gmelinite 355, 357 Iceland spar 458 Feldspar Goethite 388, 418–9 Iddingsite 8 system Ab–Or–H2O271Goldmanite 21 Illite Group 225t, 230–3 system Ab–Or–Q–H2O 272–3 Gonnardite 366 390–2, 391t system KAlSi3O8–H2O271Goslarite 437 Indialite 80 system Ab–Or–An Granophyric texture 289 Indicolite 89 solvus curtves 250, 275–6 201 Interlayer molecules 236 system Ab–Or–An–Q 284 Greigite 426 Inverse spinel 403

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Iridescence Macfallite 68 227–8 anthophyllite 145 Mackinawite 426 Namansilite 95 perthite 249, 280 Macroperthite 249 Natalyite 95 plagioclase 306 387, 402, 405, 408 Natrolite 355, 357, 366–7 Iron-a˚kermanite 73 Magnesian ilmenite 392 Nb-perovskite 400 Iron-gehlenite 73 Magnesioarfvedsonite 170 Nemalite 409 Magnesiochloritoid 48–9 Nepheline 325–33, 329t 402, 405 Magnesiochromite 402, 406, 408 Nephrite 151 Jade 151 Magnesioferrite 402, 404, 407 Niccolite 429 Jadeite 99t, 125–7 –Hastingsite 154–9 Nimite 210, 213 Jargoon 13 Magnesiohornblende–Ferrohornblende 225, 235, 237, 238 318 141t, 154–9 Norbergite 4 Jervisite 95 Magnesiokataphorite 142t Normal spinel 403 Johannsenite 95, 98t, 112–5 Magnesiokatophorite–Katophorite 167 Nosean 340-4, 342t Julgoldite 69 Magnesioriebeckite–Riebeckite Nyerereite 452 141t, 162–6 Kaersutite–Ferrokaersutite 141, 158, Magnesiostaurolite 42 Obliquity (microcline) 249 160–1 Magnesiotaramite 168 Offretite 357 Kaliophilite 327 Magnesiowu¨stite 382 Olenite 86–92,90 Kalsilite 325–33,329 Magnesite 451, 454t, 459 Oligoclase 250, 393 Kammererite 211 402, 404, 407 Olivine Group 4–11 Kanoite 95, 103, 108 Malachite 452 Olivine, serpentinization 9 Kanonaite 34 Malayaite 16–7 Omphacite 99, 100, 117, 122–4 Kaolinite Group 225t, 227–9 Manebach twinning 265–6, 298 312, 319 Kataphorite 167–8 Manganapatite 475 Opalescence 319 Katoite 21 Manganocummingtonite 148 Orthochrysotile 216 131, 315, 317 Manganogrunerite 148 Orthoclase feldspar 256, 265, 270, 16 Manganorichterite 142t 275, 278 Kidney 387 Marcasite 424 Orthopyroxene 94, 102–8 Kimzeyite 21 177 48, 49 8 Marialite 349 Oxides 382–408 Knorringite 19 Martite 387 Oxo-hornblende 156, 159 Koˆzulite 170 Maskylenite 309 Kosmochlor 99t, 125–7 Masutomilite 198 224 Kunzite 131 Meionite 349 Panunzite 326 Kushiroite 95 Melanite 21, 22, 26 Parachrysotile 218 463 Melilite Group 72–5 Paragonite 177t, 187 Kyanite 36–8 Melnikovite 426 –Ferropargasite 139t, 154–9 Merwinite 75 Parsettensite 200 Labradorescence 306 Mesh structure 221 Patch perthite 279, 281 Labradorite 250, 393 Mesolite 355, 366 Pearl 470 342 Mesoperthite 249, 260, 262 Pecoraite 220 Larnite 75 Metakaolin 228 Pectolite 132 Larvikite 280 Metamict state 13, 14, 63, 478 Peg structure 74–5 Latrappite 400 structure 174–6 Pennantite 210, 211, 213 Laumontite 355, 357, 370–1 Mica Group 174–98 Pentlandite 431 Lawsonite 65-7,244 Microcline 249, 253–9 Percussion figure 178, 192 Lazurite 340, 342 Microperthite 249, 262 Periclase 382 312 Microsommite 347 Pericline twins 265–6, 268–9, 298 Leonhardite 370 Minnesotaite 204 Peristerite 249, 306, 308 Lepidocrocite 417, 420 Moga´nite 312 Peristerite intergrowths 249, 294–5, 306 Lepidolite 177t, 179t, 190, 195–7 Molecular sieve 356, 358 Perovskite 400-1 Lepispheres 312 Monalbite 250, 258–9 Perthite(s) 249, 260, 262, 287 Leucite 334–9,336t Monazite 478–9 Petedunnite 95, 113 391 Monoclinic pyrrhotite 429 Phenakite 77 Le´vyne 357, 374 Montasite 149 Phengite 179, 183 Liddicoatite 88 4, 8 Phillipsite–Harmotome 368–9 Lithian muscovite 184, 190 225, 235, 237 Phillipsite 355 180 Mordenite 355, 377–8 Phlogopite 177t, 179t, 189–94 Lizardite 216, 219, 221t Morganite 78 Phosphates 473–9 Lo¨llingite 424 Morphology and twinning Picotite 404 Loparite-(Ce) 400 feldspars 249, 264, 297–8 Piemontite 58t, 61–2 Low microcline 256 Mukhinite 57, 61 Piezoelectric and pyroelectric Lueshite 400 37 properties (tourmaline) 87 Lusakite 40 Muscovite 177t, 179t, 181–6 Pigeonite 98t, 109–11 Myrmekite texture 289, 321 Pinite 81

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Pistomesite 461 81 Thulite 53–4, 61 Plagioclase Feldspar 292–309 Selenite 446 Tirodite 148 analyses 299t 224 Titanite 16–7 extinction angles 304–5 Sericite 231 Titanohematite 388 iridescence 306 Sericitization 232 Topaz 44–6 structure 354–9 Serpentine 216–23 Topazolite 22, 26 Plagioclase alteration 302 Serpentinization of olivine 9 Tosudite 235 Plaster of Paris 445 Shearing transformation 274 Tourmaline 86–92,90t Plasticity of clays 229 Shirozulite 190 Tremolite–Ferro-actinolite Pleochroic haloes 14, 192, 213 Si–Al ordering: orthoclase 256 139–40t, 150–3 Pleonaste 403 Siderite 451, 454t, 461–2 Trevorite 402, 405 Pollucite 334, 357 Siderophyllite 189–94 Tridymite 311–21 Polygonal serpentine 218, 219 Sideroplesite 461 Trikalsilite 326, 328 Polylithionite 195–6 Silica polymorphs 315 Trilithionite 195–6 Povondraite 88 Silica minerals 311–23 Trioctahedral chlorite 209 Prehnite 244–6,245t 358 Triple point: Al2SiO5 31, 36 Protoenstatite 100, 102-103, 105 Sillimanite 30–2, 37t 429 Pseudobrookite 399 Silvialite 353 Tschermakite–Ferrotschermakite Pseudoleucite 289, 334, 336 Smectite 226, 230 139t, 154–9 Pseudowollastonite 133, 135 Smectite Group 234–8 ‘Tschermak’ component 101 Pumpellyite 68–71,69t 452 Turbidity (feldpars) 277, 280–1 Pyrite 424–8 317 Tweed microstructure Pyromorphite 440 Soda melilite 72-73 250, 257, 272, 288 Pyrope 18–20 Sodalite Group 340-4, 342t Twin laws (feldspars) 264–6 390–1 162 Two feldspar geothermometer 251 Pyrophyllite 202–3,235 Sodium feldspars 259, 268, 299t, Group 94–131 306, 309 Ugrandite 21 Pyroxene geothermobarometry 104 Specularite 387 Ultramarine 342 133 Spessartine 18, 20, 22 Ulvo¨spinel 402, 405 Pyrrhotite 429–31 Sphaerosiderite 461 Undulatory extinction 317 Sphalerite 435-8 Uralite 153, 159 Quartz 311–3, 315–8,320 Spinel twin law 403, 406 Uvarovite 18, 20, 21, 22 twin laws 317 402–8, 405t Uvite 86–92,90t rotary polarization 317 Spinel (sensu stricto) 403–4, 406–7 Spinodal decomposition 276 Vaesite 424 Rectorite 235 Spodumene 99t, 131 Vaterite 451 Reedmergnerite 271 Spurrite 75 Verdelite 89 13 Staining technique 451–2, 457 Vermiculite 225–6, 230, 239–41 451, 454t Staining feldspar 282 Vesuvianite 28–9 120, 133 Star-sapphires 385 Viridine 34, 35, 37 Rombic section; feldspar 266–8 Staurolite 39–43 Vishnevite 345–8 Richterite–Ferrorichterite 142t, 167–8 Stilbite 355–7 Riebeckite 142t, 162–6 Stilpnomelane 199–201 Wairakite 357, 363–4 Rose quartz 317 312, 315, 320 Willemseite 204 Rose muscovite 182, 184, 196 Stru¨verite 394 Wiluite 28 Rossmanite 88 Strontianite 454t, 471–2 Winchite 139, 167 Rubellite 89, 91 Sudoite 211, 213 Withamite 61 270 Sulphates 441–9 Witherite 451, 454t, 472 Ruby 384 Sulphur 444, 447 Wollastonite 132–5 Rutile 393–5,394t Sulphides 423–40 Wood tin 383 Sursassite 68 Wurtzite 435–8 Sanidine twinning 253–8, 270t, Sylvite 483 Wu¨stite 382 282, 287 225, 235, 237 Talc 204–7,235 Xonotlite 28, 133 Sapphire 384–5 Tanzanite 54 Sapphirine 133, 386 Taramite 139, 167–8 Yttrofluorite 480 Satin spar 447 Tarnowitzite 468 Yttrotitanite 16 Sauconite 234, 235, 237, 238 Tartan twinning (alkali feldspar) 248, Scapolite 26, 349–53,352t 259, 266, 268, 288 Group 355–79 Schiller 280, 306 Tawmawite 53, 57 analyses 359 Schorl 86–92,90t Tephroite 8 structures 357 Schorlomite 20, 21, 22, 26 Tetraferriannite 190 Zinnwaldite 177, 195, 198 Scolecite 366 Tetraferriphlogopite 190 Zircon 12–4 Sector twinning 22, 83, 119 Tetrakalsilite 326, 328 Zoisite 53–5,58t 312, 320 355–6

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