Cristobalite

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Caspar quarry, Bellerberg volcano, Ettringen, Mayen, Eifel, Rhineland-Palatinate, Germany
© Fred Kruijen

Show Cristobalite Photos (78)

Formula:

SiO

System:

Tetragonal

Colour:

Blue grey, brown, grey, ...

Lustre:

Vitreous

Hardness:

6 - 7

Name:

Named after its locality (Cerro San Cristobal, Mexico)

Polymorph of:

Coesite, Quartz, Stishovite, Tridymite

Post-volcanic, magmatic, and secondary.

May be intergrown with Tridymite.

Classification of Cristobalite

IMA status:

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"

Strunz 8th edition ID:

4/D.01-30

Nickel-Strunz 10th (pending) edition ID:

4.DA.15

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
A : With small cations: Silica family

Dana 8th edition ID:

75.1.1.1

75 : TECTOSILICATES Si Tetrahedral Frameworks
1 : Si Tetrahedral Frameworks - SiO₂ with [4] coordinated Si

Hey's CIM Ref.:

7.8.5

7 : Oxides and Hydroxides
8 : Oxides of Si

mindat.org URL:

http://www.mindat.org/min-1155.html
Please feel free to link to this page.

Type Occurrence of Cristobalite

Type Locality:

Cerro San Cristóbal, Mun. de Pachuca, Hidalgo, Mexico

Year of Discovery:

1887

Occurrences of Cristobalite

Geological Setting:

In vesicles and lithophysae

Physical Properties of Cristobalite

Lustre:

Vitreous

Diaphaneity (Transparency):

Transparent

Colour:

Blue grey, brown, grey, yellow, or white

Streak:

White

Hardness (Mohs):

6 - 7

Tenacity:

Brittle

Density (measured):

2.32 - 2.36 g/cm³

Density (calculated):

2.33 g/cm³

Crystallography of Cristobalite

Crystal System:

Tetragonal

Class (H-M):

4 2 2 - Trapezohedral

Space Group:

P4₁ 2₁ 2

Cell Parameters:

a = 4.9709(1) Å, c = 6.9278(2) Å

Ratio:

a:c = 1 : 1.394

Unit Cell Volume:

V 171.18 Å³ (Calculated from Unit Cell)

Morphology:

Pseudo octahedral crystals, commonly dendritic, spherulites.

Twinning:

On {111}

Crystal Atlas:

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Cristobalite no.1 - Goldschmidt (1913-1926)

About Crystal Atlas

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The mindat.org Crystal Atlas allows you to view a selection of crystal drawings of real and idealised crystal forms for this mineral and, in certain cases, 3d rotating crystal objects. You need Java to see these. You can download Java for free - click here to download Java

The 3d models and java code are kindly provided by www.smorf.nl. You can control the movement of the models by holding down the left mouse-button over the 3d model and moving your mouse. Keyboard controls are:

: default positions

t/T	: decrease/increase transparency	x/X	: next/previous texture
b/B	: next/previous background	w	: toggle wireframe
s	: toggle sticks	m	: toggle miller indices
k	: toggle crystallographic axes	=/-	: zoom in/out
r	: stop/start rotation	1/2/3

X-Ray Powder Diffraction:

d-spacing		Intensity
4.05		(100)
3.135		(11)
2.841		(13)
2.485		(20)
2.465		(5)
2.118		(5)
1.870		(7)

Comments:

For synthetic material.

Optical Data of Cristobalite

Type:

Uniaxial (-)

RI values:

n_ω = 1.487 n_ε = 1.484

Maximum Birefringence:

δ = 0.003

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.

Surface Relief:

Moderate

Chemical Properties of Cristobalite

Formula:

SiO

Essential elements:

O, Si

All elements listed in formula:

O, Si

Common Impurities:

Fe,Ca,Al,K,Na,Ti,Mn,Mg,P

Relationship of Cristobalite to other Species

4.DA.05

Quartz

SiO

4.DA.10

Opal

SiO

· nH

4.DA.10

Tridymite

SiO

4.DA.20

Mogánite

SiO

4.DA.25

Melanophlogite

46SiO

· 6(N

,CO

) · 2(CH

)

4.DA.30

Lechatelierite

SiO

4.DA.35

Coesite

SiO

4.DA.40

Stishovite

SiO

4.DA.45

Keatite

4.DA.50

Seifertite

SiO

7.8.1

Quartz

SiO

7.8.2

Coesite

SiO

7.8.3

Tridymite

SiO

7.8.4

Stishovite

SiO

7.8.6

Lechatelierite

SiO

7.8.7

Silhydrite

3SiO

· H

7.8.8

Opal

SiO

· nH

7.8.9

Mogánite

SiO

Other Names for Cristobalite

Synonyms:

Other Languages:

Dutch:	Cristobaliet
Estonian:	Kristobaliit
French:	Cristobalite
German:	Cristobalit α-Cristobalit b-Cristobalit Cristobalitchalcedon Lussatit Tiefcristobalit
Italian:	Cristobalite
Japanese:	クリストバライト
Polish:	Krystobalit
Portuguese:	Cristobalita

Romanian:	Cristobalit
Russian:	Кристобалит
Simplified Chinese:	方英石白矽石
Spanish:	α-Cristobalita b-Cristobalita Cristobalita Lussatita
Ukrainian:	Кристобаліт

Other Information

Thermal Behaviour:

Inverts from high cristobalite at 268C.

Health Warning:

No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Cristobalite

Reference List:

- +

Murdoch, Joseph (1942), Crystallographic notes, cristobalite, stephanite, natrolite: Am. Min.: 27: 500-506.

Henderson, J.H., M.L. Jackson, J.K. Syers, R.N. Clayton & R.W. Rex (1971), Cristobalite Authigenic origin in relation to montmorillonite and quartz origin in bentonite: Clays and Clay Minerals: 19: 229-238.

Murata, K.J. & J.K. Nakata (1974), Cristobalite stage in the diagenesis of diatomaceous shale: Science: 184: 567-568.

Richet, P., Bottinga, Y., Deniélou, L., Petitet, J.P., and Téqui, C. (1982) Thermodynamic properties of quartz, cristobalite, and amorphous SiO2: drop calorimetry measurements between 1000 and 1800 K and a review from 0 to 2000 K. Geochimica et Cosmochmica Acta: 46: 2639-2658.