Cristobalite Mineral Data

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.

Name Pronunciation:

Cristobalite + Pronunciation

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 - Trapezohedral H-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),

Physical Properties of Cristobalite

Cleavage:

None

Color:

Blue gray, Brown, Gray, Yellow, White.

Density:

2.27

Diaphaneity:

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:

Fluorescent, Short UV=green red, Long UV=reen red.

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
Ncalc = 1.47 - 1.48

Optical Data:

Isotropic, n=1.485-1.487.

Calculated Properties of Cristobalite

Electron Density:

Bulk Density (Electron Density)=2.33 gm/cc
note: Specific Gravity of Cristobalite =2.33 gm/cc.

Fermion Index:

Fermion Index = 0.02
Boson Index = 0.98

Photoelectric:

PE_Cristobalite= 1.80 barns/electron
U=PE_Cristobalite x rElectron Density= 4.18 barns/cc.

Radioactivity:

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

Cristobalite Classification

Dana Class:

75.01.01.01 (75)Tectosilicate Si Tetrahedral Frameworks

(75.01)SiO2 with [4] coordinated Si

(75.01.01)Dana Group

75.01.01.01 Cristobalite SiO2 P 4₁2₁2 4 2 2

Strunz Class:

04.DA.15 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.15 Cristobalite SiO2 P 4₁2₁2 4 2 2

Other Cristobalite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Collectors Book of Fluorescent Minerals) OPTIC PROP.(Heinrich65)

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Cristobalite

SiO2
Dana No: 75.01.01.01 Strunz No: 04.DA.15
Locality:

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