Tridymite Mineral Data

General Tridymite Information

Chemical Formula:

SiO2

Composition:

Molecular Weight = 60.08 gm

Silicon 46.74 % Si 100.00 % SiO₂

Oxygen 53.26 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

(SiO₂)

Environment:

Cavities in volcanic rocks.

IMA Status:

Valid Species (Pre-IMA) 1868

Locality:

Occurs world wide. Link to MinDat.org Location Data.

Name Origin:

From the Greek Tridymos - "triplex."

Name Pronunciation:

Tridymite + Pronunciation

Tridymite Image

Images:

Tridymite

Comments: Clear, pseudohexagonal crystals of tridymite on matrix.
Location: Bellerberg quarry, Laacher See, Rhineland-Palatinate, Germany. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Tridymite Crystallography

Axial Ratios:

a:b:c =0.5769:1:4.7551

Cell Dimensions:

a = 9.932, b = 17.216, c = 81.864, Z = 330; alpha = 90°, beta = 90°, gamma = 90° V = 13,997.87 Den(Calc)= 2.35

Crystal System:

Triclinic - PedialH-M Symbol (1) Space Group: F1

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

By Intensity(I/I_o): 4.107(1), 4.328(0.9), 3.818(0.5),

Crystal Structure:

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Dollase W A , Baur W H , American Mineralogist , 61 (1976) p.971-978, The superstructure of meteoritic low tridymite solved by computer simulation

View Additional jPOWD Structure files for Tridymite
[1] [2] [3] [4]

Physical Properties of Tridymite

Cleavage:

{0001} Indistinct, {1010} Imperfect

Color:

Colorless, White, Yellowish white, Gray.

Density:

2.28 - 2.33, Average = 2.3

Diaphaneity:

Transparent to translucent

Fracture:

Brittle - Conchoidal - Very brittle fracture producing small, conchoidal fragments.

Habit:

Platy - Sheet forms (e.g. micas).

Habit:

Spherical - Spherical, rounded aggregates.

Hardness:

6.5-7 - Pyrite-Quartz

Luminescence:

Fluorescent, Short UV=dark cherry red.

Luster:

Vitreous (Glassy)

Magnetism:

Nonmagnetic

Streak:

white

Optical Properties of Tridymite

Gladstone-Dale:

CI meas= 0.002 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.021 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2035,KPDmeas= 0.2075,KC= 0.208
Ncalc = 1.47 - 1.49

Optical Data:

Biaxial (+), a=1.471-1.482, b=1.472-1.483, g=1.474-1.488, bire=0.0030-0.0060, 2V(Calc)=50-72, 2V(Meas)=36-90. Dispersion none.

Pleochroism (x):

colorless.

Pleochroism (y):

colorless.

Pleochroism (z):

colorless.

Calculated Properties of Tridymite

Electron Density:

Bulk Density (Electron Density)=2.30 gm/cc
note: Specific Gravity of Tridymite =2.31 gm/cc.

Fermion Index:

Fermion Index = 0.02
Boson Index = 0.98

Photoelectric:

PE_Tridymite= 1.80 barns/electron
U=PE_Tridymite x rElectron Density= 4.14 barns/cc.

Radioactivity:

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

Tridymite Classification

Dana Class:

75.01.02.01 (75)Tectosilicate Si Tetrahedral Frameworks

(75.01)SiO2 with [4] coordinated Si

(75.01.02)Dana Group

75.01.02.01 Tridymite SiO2 F1 1

Strunz Class:

04.DA.10 04 - OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodate

04.D - Metal:Oxygen = 1:2 and similar

04.DA -With small cations

04.DA.10 Opal SiO2•n(H2O) None

04.DA.10 Tridymite SiO2 F1 1

Other Tridymite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Collectors Book of Fluorescent Minerals) OPTIC PROP.(Larousse des Mineraux,1981)

See Also:

Links to other databases for Tridymite :
1 - Am. Min. Crystal Structure Database
2 - Amethyst Galleries' Mineral Gallery
3 - Athena
4 - GeoScienceWorld
5 - Google Images
6 - Google Scholar
7 - Handbook of Mineralogy (MinSocAm)
8 - Handbook of Mineralogy (UofA)
9 - MinDAT
10 - Mineral and Gemstone Kingdom
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info
15 - WWW-MINCRYST

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Ask about Tridymite here :
Ask-A-Mineralogist from the Mineralogical Society of America
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Print or Cut-and-Paste your Tridymite Specimen Label here :

Tridymite

SiO2
Dana No: 75.01.02.01 Strunz No: 04.DA.10
Locality:

Notes: