Topaz Mineral Data

General Topaz Information

Chemical Formula:

Al2SiO4(F,OH)2

Composition:

Molecular Weight = 182.25 gm

Aluminum 29.61 % Al 55.95 % Al₂O₃

Silicon 15.41 % Si 32.97 % SiO₂

Hydrogen 0.50 % H 4.45 % H₂O

Oxygen 43.02 % O

Fluorine 11.47 % F 11.47 % F

- % F -4.83 % -O=F₂

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Al₂(SiO₄)F_1.1(OH)_0.9

Environment:

Pegmatites and high temperature quartz veins. Cavities in granites and rhyolites. Deposited by fluorine-rich vapors in rocks of rhyolite composition.

IMA Status:

Valid Species (Pre-IMA) Prehistoric

Locality:

Topasos Island in the Red Sea. Link to MinDat.org Location Data.

Name Origin:

Named after its locality.

Name Pronunciation:

Topaz

Synonym:

Pycnite - yellowish white-

Topaz Image

Images:

Topaz

Comments: Transparent sharp gem topaz crystal set upon a matrix of crystallized white albite and silvery muscovite.
Location: Yunu Village, Shigar, Gilgit division, Pakistan. Scale: 1.6 x 1.8 x 4.2 cm.
© Dan Weinrich

Topaz Crystallography

Axial Ratios:

a:b:c =0.4943:1:0.9545

Cell Dimensions:

a = 4.35, b = 8.8, c = 8.4, Z = 4; V = 321.55 Den(Calc)= 3.76

Crystal System:

Orthorhombic - Dipyramidal H-M Symbol (2/m 2/m 2/m) Space Group: Pbnm

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 2.937(1), 3.195(0.65), 3.369(0.6),

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Forms: ( 0 1 0) ( 0 2 1) ( 1 1 1) ( 0 1 1) ( 1 1 2) ( 1 2 0) ( 1 1 0) ( 0 0 1)

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Physical Properties of Topaz

Cleavage:

{001} Perfect

Color:

Colorless, Pale blue, Yellow, Yellowish brown, Red.

Density:

3.5 - 3.6, Average = 3.55

Diaphaneity:

Transparent

Fracture:

Brittle - Uneven - Very brittle fracture producing uneven fragments.

Habit:

Crystalline - Coarse - Occurs as well-formed coarse sized crystals.

Habit:

Massive - Granular - Common texture observed in granite and other igneous rock.

Habit:

Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).

Hardness:

8 - Topaz

Luminescence:

Fluorescent, Short UV=golden yellow, Long UV=cream.

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Topaz

Gladstone-Dale:

CI meas= 0.146 (Poor) - where the CI = (1-KPDmeas/KC)
CI calc= 0.193 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1653,KPDmeas= 0.1751,KC= 0.2049
Ncalc = 1.72 - 1.77

Optical Data:

Biaxial (+), a=1.606-1.629, b=1.609-1.631, g=1.616-1.638, bire=0.0090-0.0100, 2V(Calc)=58-68, 2V(Meas)=48-68. Dispersion noticeable, r > v.

Pleochroism (x):

colorless.

Pleochroism (y):

colorless.

Calculated Properties of Topaz

Electron Density:

Bulk Density (Electron Density)=3.51 gm/cc
note: Specific Gravity of Topaz =3.55 gm/cc.

Fermion Index:

Fermion Index = 0.0074038512
Boson Index = 0.9925961488

Photoelectric:

PE_Topaz= 1.53 barns/electron
U=PE_Topaz x rElectron Density= 5.36 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Topaz is Not Radioactive

Topaz Classification

Dana Class:

52.03.01.01 (52)Nesosilicate Insular SiO4 Groups and O, OH, F, and H2O

(52.03)with cations in [6] coordination only

(52.03.01)Topaz Group

52.03.01.01 Topaz Al2SiO4(F,OH)2 Pbnm 2/m 2/m 2/m

52.03.01.02 Krieselite! (Al,Ga)2(Ge,C)O4(OH)2 P nma 2/m 2/m 2/m

Strunz Class:

09.AF.35 09 - SILICATES (Germanates)

09.A - Nesosilicates

09.AF -Nesosilicates with additional anions;

09.AF.35 Topaz Al2SiO4(F,OH)2 Pbnm 2/m 2/m 2/m

09.AF.35 Krieselite! (Al,Ga)2(Ge,C)O4(OH)2 P nma 2/m 2/m 2/m

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Topaz

Al2SiO4(F,OH)2
Dana No: 52.03.01.01 Strunz No: 09.AF.35
Locality:

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