Cristobalite Mineral Data

Cristobalite Mineral Data +

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General Cristobalite 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:

Post-volcanic, magmatic, and secondary.

IMA Status:

Valid Species (Pre-IMA) 1887

Locality:

Cerro San Cristobal, Mexico. Link to MinDat.org Location Data.

Name Origin:

Named after its locality.

Cristobalite Image

Images:

Cristobalite

Comments: White crystals of cristobalite frozen in obsidian glass.
Location: Cerro San Cristobal, Pachuca, Hidalgo, Mexico. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Cristobalite Crystallography

Axial Ratios:

a:c = 1:1.39167

Cell Dimensions:

a = 4.971, c = 6.918, Z = 4; V = 170.95 Den(Calc)= 2.33

Crystal System:

Tetragonal - TrapezohedralH-M Symbol (4 2 2) Space Group: P 4₁2₁2

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

By Intensity(I/I_o): 4.05(1), 2.485(0.2), 2.841(0.13),

Crystal Structure:

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Downs R T , Palmer D C , American Mineralogist , 79 (1994) p.9-14, The pressure behavior of alpha cristobalite, P = room pressure

View Additional jPOWD Structure files for Cristobalite
[1] [10] [11] [12] [13] [14] [15] [16] [17] [18] [2] [3] [4] [5] [6] [7] [8] [9]

Physical Properties of Cristobalite

Cleavage:

None

Color:

Blue gray, Brown, Gray, Yellow, White.

Density:

2.27

Diaphaniety:

Translucent to transparent

Fracture:

Brittle - Generally displayed by glasses and most non-metallic minerals.

Habit:

Crystalline - Fine - Occurs as well-formed fine sized crystals.

Habit:

Spherical - Spherical, rounded aggregates.

Hardness:

6.5 - Pyrite

Luminescence:

Non-fluorescent.

Luster:

Vitreous (Glassy)

Magnetism:

Nonmagnetic

Streak:

white

Optical Properties of Cristobalite

Gladstone-Dale:

CI meas= -0.03 (Excellent) - where the CI = (1-KPDmeas/KC)
CI calc= -0.004 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2088,KPDmeas= 0.2143,KC= 0.208

Optical Data:

Isotropic, n=1.485-1.487.

Calculated Properties of Cristobalite

Electron Density:

r_electron=2.33 gm/cc
note: r_Cristobalite=2.33 gm/cc.

Fermion Index

Fermion Index = 0.02208
Boson Index = 0.97792

Photoelectric:

PE_Cristobalite= 1.80 barns/electron
U=PE_Cristobalite x r_electron= 4.18 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Cristobalite is Not Radioactive

Cristobalite Classification

Dana Class:

75.1.1.1 (75)Tectosilicate Si Tetrahedral Frameworks

(75.1)SiO2 with [4] coordinated Si

(75.1.1)Dana Group

75.1.1.1 Cristobalite SiO2 P 4₁2₁2 4 2 2

Strunz Class:

IV/D.01-30 IV - Oxides

IV/D - Oxides with metal : oxygen = 1:2 (MO2 and related compounds)

IV/D.01 - Quartz group

IV/D.01-10 Quartz SiO2 P 3₁21,P 3₂21 3 2

IV/D.01-20 Tridymite SiO2 F1 1

IV/D.01-30 Cristobalite SiO2 P 4₁2₁2 4 2 2

IV/D.01-35 Moganite! SiO2 I2/a 2/m

IV/D.01-40 Melanophlogite SiO2·n(C,H,O,S) P 4₁/nbc 4/m 2/m 2/m

IV/D.01-40* Melanophlogite-beta! SiO2·n(C,H,O,S) P m3n 4/m 3 2/m

IV/D.01-50 Coesite SiO2 C 2/c 2/m

IV/D.01-60 Stishovite SiO2 P 4/mnm 4/m 2/m 2/m

IV/D.01-70 Lechatelierite* SiO2 None

IV/D.01-80 Opal SiO2·n(H2O) None

Other Cristobalite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Heinrich65)

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Print or Cut-and-Paste your Cristobalite Specimen Label here :

Cristobalite

SiO2
Dana No: 75.1.1.1 Strunz No: IV/D.01-30
Locality:

Notes: