Tacharanite Mineral Data

Tacharanite Mineral Data +

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General Tacharanite Information

Chemical Formula:

Ca12Al2Si18O33(OH)36

Composition:

Molecular Weight = 2,180.68 gm

Calcium 22.05 % Ca 30.86 % CaO

Aluminum 2.47 % Al 4.68 % Al₂O₃

Silicon 23.18 % Si 49.60 % SiO₂

Hydrogen 1.66 % H 14.87 % H₂O

Oxygen 50.62 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Ca₁₂Al₂Si₁₈O₃₃(OH)₃₆

Environment:

In vesicles or fractures in dolorites or other basic igneous rocks.

IMA Status:

Approved IMA 1961

Locality:

Portree, Isle of Skye, Scotland. Link to MinDat.org Location Data.

Name Origin:

Named from the Gaelic "tacharan," a changeling, because on standing in air the mineral breaks down to form other compounds (not noticed by later investigators).

Tacharanite Image

Images:

Tacharanite Phillipsite

Comments: Spherical tacharanite aggregates on phillipsite crystals.
Location: Espalion, Aveyron, France. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Tacharanite Crystallography

Axial Ratios:

a:b:c =4.6767:1:7.6438

Cell Dimensions:

a = 17.07, b = 3.65, c = 27.9, Z = 1; beta = 114.1° V = 1,586.80 Den(Calc)= 2.28

Crystal System:

MonoclinicSpace Group: A centered

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

By Intensity(I/I_o): 12.7(1), 3.05(0.8), 2.89(0.7),

Physical Properties of Tacharanite

Color:

White.

Density:

2.21 - 2.36, Average = 2.28

Fracture:

Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).

Habit:

Cryptocrystalline - Occurs as crystals too small to distinguish with the naked eye.

Hardness:

5 - Apatite

Luster:

Earthy (Dull)

Streak:

white

Optical Properties of Tacharanite

Gladstone-Dale:

CI meas= -0.012 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= -0.014 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2314,KPDmeas= 0.2309,KC= 0.2282

Optical Data:

Biaxial (+), a=1.518-1.525, g=1.53-1.537, bire=0.0120

Calculated Properties of Tacharanite

Electron Density:

r_electron=2.32 gm/cc
note: r_Tacharanite=2.29 gm/cc.

Fermion Index

Fermion Index = 0.01136
Boson Index = 0.98864

Photoelectric:

PE_Tacharanite= 3.66 barns/electron
U=PE_Tacharanite x r_electron= 8.49 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Tacharanite is Not Radioactive

Tacharanite Classification

Dana Class:

72.3.2.6 (72)Phyllosilicate Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings

(72.3)with 3-, 4-, or 5-membered rings and 8-membered rings

(72.3.2)Tobermorite group (5- & 8-membered rings)

72.3.2.1 Tobermorite Ca5Si6O16(OH)2·4(H2O) C 222₁ 2 2 2

72.3.2.2 Clinotobermorite Ca5Si6(O,OH)18·5(H2O) Cc,C 2/c Mono

72.3.2.3 Plombierite Ca5H2Si6O18·6(H2O)(?) C 222₁ 2 2 2

72.3.2.4 Riversideite Ca5Si6O16(OH)2·2(H2O) B2212 2 2 2

72.3.2.5 Okenite Ca3[Si6O15]·6(H2O) P1 or P1 Tri

72.3.2.6 Tacharanite Ca12Al2Si18O33(OH)36 A centered Mono

72.3.2.7 Nekoite Ca3Si6O15·7(H2O) P1 1

72.3.2.8 Oyelite Ca10B2Si8O29·12(H2O) B**** Ortho

Strunz Class:

VIII/F.21-40 VIII - Silicates

VIII/F - Inosilicates (chain and band) Triplet chains [Si6O15/17]6-/10- and modified triplet bands

VIII/F.21 - Nekoite - Tacharanite series

VIII/F.21-10 Nekoite Ca3Si6O15·7(H2O) P1 1

VIII/F.21-20 Scawtite Ca7Si6(CO3)O18·2(H2O) C 2/m 2/m

VIII/F.21-30 Xonotlite Ca6Si6O17(OH)2 P 2/a 2/m

VIII/F.21-40 Tacharanite Ca12Al2Si18O33(OH)36 A centered Mono

Other Tacharanite Information

References:

NAME( Dana8) PHYS. PROP.(Dana8) OPTIC PROP.(Dana8)

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Tacharanite

Ca12Al2Si18O33(OH)36
Dana No: 72.3.2.6 Strunz No: VIII/F.21-40
Locality:

Notes: