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Diopside

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Formula:
CaMgSi2O6
System:
Monoclinic
Colour:
light to dark green, ...
Lustre:
Vitreous, Dull
Hardness:
5½ - 6½
Name:
Named in 1806 by Rene Just Haüy From the Greek διζ- for "double" and οψτζ- "appearance," in allusion to two possible orientations of the prism zone.
Pyroxene Group - Clinopyroxene Subgroup; see also the Diopside-Hedenbergite Series, and the Diopside-Johannsenite Series.

One of the most common members of the Pyroxene Group. Often occurs in metamorphosed limestones (marbles) as generally pale greenish to greyish green crystals, masses and blebs/grains associated with humite-group minerals, spinel, phlogopite, tremolite and grossular. Can also be pure white and not distinguishable from the enclosing carbonate. Often fluorescent bright powder blue.

Visit gemdat.org for gemological information about Diopside.

Classification of Diopside

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
9.DA.15

9 : SILICATES (Germanates)
D : Inosilicates
A : Inosilicates with 2-periodic single chains, Si2O6; pyroxene family
65.1.3a.1

65 : INOSILICATES Single-Width,Unbranched Chains,(W=1)
1 : Single-Width Unbranched Chains, W=1 with chains P=2
14.6.12

14 : Silicates not Containing Aluminum
6 : Silicates of Ca with alkali or Mg or both
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Physical Properties of Diopside

Vitreous, Dull
Diaphaneity (Transparency):
Transparent, Opaque
Colour:
light to dark green, blue, brown, colourless, snow white, grey
Streak:
white
Hardness (Mohs):
5½ - 6½
Tenacity:
Brittle
Cleavage:
Distinct/Good
on {110}
Parting:
on {100} and probably {010}
Fracture:
Irregular/Uneven, Conchoidal
Density:
3.22 - 3.38 g/cm3 (Measured)    3.278 g/cm3 (Calculated)

Crystallography of Diopside

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/b
Cell Parameters:
a = 9.746Å, b = 8.899Å, c = 5.251Å
β = 105.79°
Ratio:
a:b:c = 1.095 : 1 : 0.59
Unit Cell Volume:
V 438.23 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Prismatic crystals with square cross sections.
Twinning:
Simple or multiple twins on {100} or {010} common.

Crystallographic forms of Diopside

Crystal Atlas:
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Diopside no.135 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by www.smorf.nl.

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Edge Lines | Miller Indicies | Axes

Transparency
Opaque | Translucent | Transparent

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Along a-axis | Along b-axis | Along c-axis | Start rotation | Stop rotation
X-Ray Powder Diffraction:
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Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Optical Data of Diopside

Type:
Biaxial (+)
RI values:
nα = 1.663 - 1.699 nβ = 1.671 - 1.705 nγ = 1.693 - 1.728
2V:
Measured: 58° to 63°, Calculated: 56° to 64°
Max Birefringence:
δ = 0.030
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
High
Dispersion:
weak to distinct r > v

Chemical Properties of Diopside

Formula:
CaMgSi2O6
Essential elements:
All elements listed in formula:
Common Impurities:
Fe,V,Cr,Mn,Zn,Al,Ti,Na,K

Relationship of Diopside to other Species

Series:
Forms a series with Johannsenite (see here)
Forms a series with Hedenbergite (see here)
Forms a series with Kosmochlor (see here)
Other Members of Group:
AegirineNaFe3+Si2O6
Aegirine-augite(Na,Ca)(Fe3+,Fe2+,Mg,Al)Si2O6
Augite(Ca,Na)(Mg,Fe2+,Al,Fe3+,Ti)[(Si,Al)2O6]
ClinoenstatiteMgSiO3
ClinoferrosiliteFe2+SiO3
EsseneiteCaFe3+[AlSiO6]
GrossmaniteCaTi3+ AlSiO6
HedenbergiteCaFe2+Si2O6
JadeiteNa(Al,Fe3+)Si2O6
Jervisite(Na,Ca,Fe2+)(Sc,Mg,Fe2+)Si2O6
JohannseniteCaMn2+Si2O6
KanoiteMn2+(Mg,Mn2+)Si2O6
KosmochlorNaCrSi2O6
KushiroiteCaAl[AlSiO6]
NamansiliteNaMn3+Si2O6
NatalyiteNa(V3+,Cr)Si2O6
Omphacite(Ca,Na)(Mg,Al)Si2O6
PetedunniteCa(Zn,Mn2+,Mg,Fe2+)Si2O6
Pigeonite(Mg,Fe2+,Ca)(Mg,Fe2+)Si2O6
SpodumeneLiAlSi2O6
9.DA.05Donpeacorite(Mn2+,Mg)Mg[SiO3]2
9.DA.05EnstatiteMgSiO3
9.DA.05FerrosiliteFeSiO3
9.DA.10ClinoenstatiteMgSiO3
9.DA.10ClinoferrosiliteFe2+SiO3
9.DA.10KanoiteMn2+(Mg,Mn2+)Si2O6
9.DA.10Pigeonite(Mg,Fe2+,Ca)(Mg,Fe2+)Si2O6
9.DA.15Augite(Ca,Na)(Mg,Fe2+,Al,Fe3+,Ti)[(Si,Al)2O6]
9.DA.15EsseneiteCaFe3+[AlSiO6]
9.DA.15HedenbergiteCaFe2+Si2O6
9.DA.15JohannseniteCaMn2+Si2O6
9.DA.15PetedunniteCa(Zn,Mn2+,Mg,Fe2+)Si2O6
9.DA.15DavisiteCaScAlSiO6
9.DA.15KushiroiteCaAl[AlSiO6]
9.DA.15GrossmaniteCaTi3+ AlSiO6
9.DA.20Aegirine-augite(Na,Ca)(Fe3+,Fe2+,Mg,Al)Si2O6
9.DA.20Omphacite(Ca,Na)(Mg,Al)Si2O6
9.DA.25AegirineNaFe3+Si2O6
9.DA.25JadeiteNa(Al,Fe3+)Si2O6
9.DA.25Jervisite(Na,Ca,Fe2+)(Sc,Mg,Fe2+)Si2O6
9.DA.25KosmochlorNaCrSi2O6
9.DA.25NamansiliteNaMn3+Si2O6
9.DA.25NatalyiteNa(V3+,Cr)Si2O6
9.DA.30SpodumeneLiAlSi2O6
14.6.1CombeiteNa2Ca2(Si6O18)0.5
14.6.2PectoliteNaCa2(HSi3O9)
14.6.3Pectolite-M2abcNaCa2[HSi3O9]
14.6.4DenisoviteCa2(K,Na)Si3O8(F,OH)2
14.6.5TokkoiteK2Ca4Si7O17(O,OH,F)4
14.6.6MountainiteKNa2Ca2[Si8O19(OH)] · 6H2O
14.6.7RhodesiteKHCa2Si8O19 · 5H2O
14.6.8MiseriteK(Ca,Ce)4Si5O13(OH)3
14.6.9ÅkermaniteCa2Mg(Si2O7)
14.6.10MonticelliteCaMgSiO4
14.6.11MerwiniteCa3Mg(SiO4)2
14.6.13Tremolite☐{Ca2}{Mg5}(Si8O22)(OH)2

Other Names for Diopside

Other Information

Bright blue-white (white coloured material)(SW UV)
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Diopside

Reference List:
Smith, J.V. (1966) X-ray emission microanalysis of rock-forming minerals. VI: Clinopyroxenes near the diopside-hedenbergite join. Journal of Geology: 74: 463-467.

Clark, J.R., D.E. Appleman, and J.J. Papike (1969) Crystal-chemical characterization of clinopyroxenes based on eight new structure refinements. MSA Special Paper 2: 31-50.

Ghose, S. & P. Schindler (1969), Determination of the distribution of trace amounts on Mn+2 in diopsides by electron paramagnetic resonance. In: Pyroxenes and Amphiboles: Crystal chemistry and phase petrology: Mineralogical Society of America Special Paper 2: 51-58.

Kushiro, I. (1969), The system forsterite-diopside-silica with and without water at high pressures: American Journal of Science: 267: 269-294.

Cameron, M., S. Shigeho, C.T. Prewitt & J.J. Papike (1973), High temperature crystal chemistry of acmite, diopside, hedenbergite, jadeite, spodumene and ureyite: American Mineralogist: 58: 594-618.

A. Mottana, G. Rossi, A. Kracher, G. Kurat (1979): Violan revisited: Mn-bearing omphacite and diopside. Tschermaks mineralogische und petrographische Mitteilungen 26, 187-201.

Levien, L. and Prewitt, C.T. (1981) High pressure structural study of diopside. American Mineralogist: 66: 315-323.

Rossi, G., Smith, D.C., Ungaretti, L., and Domeneghetti, M.C. (1983) Crystal-chemistry and cation ordering in the system diopside-jadeite: a detailed study by crystal structure refinement. Contributions to Mineralogy and Petrology: 83: 247-258.

Richet, P. and Bottinga, Y. (1984b) Anorthite, andesine, wollastonite, diopside, cordierite, and pyrope thermodynamics of melting, glass transitions, and properties of the amorphous phases. Earth and Planetary Science Letters: 67: 415-432.

Johnson, K.T.M., Dick, H.J.B., and Shimizu, N. (1990) Melting in the oceanic upper mantle: an ion microprobe study of diopsides in abyssal peridotites. Journal of Geophysical Research: 95: 2661-2678.

Raterron, P. & O. Jaoul (1991), High-temperature deformaton of diopside single crystal, 1., Mechanical data: Journal of Geophysical Research, B, Solid Earth and Planets: 96: 14277-14286.

Knoche, R., Dingwell, D.B., and Webb, S.L. (1992a) Non-linear temperature dependence of liquid volumes in the system albite-anorthite-diopside. Contributions to Mineralogy and Petrology: 111: 61-73.

Knoche, R., Dingwell, D.B., and Webb, S.L. (1992b) Temperature-dependent thermal expansivities of silicate melts: The system anorthite-diopside. Geochimica et Cosmochimica Acta: 56: 689-699.

Harlow, G.E. (1996) Structure refinement of a natural K-rich diopside: the effect of K on the average structure. American Mineralogist: 81: 632-638.

Courtial, P., Téqui, C., and Richet, P. (2000) Thermodynamics of diopside, anorthite, pseudowollastonite, CaMgGeO4 olivine, and åkermanite up to near the melting point. Physics and Chemistry of Minerals: 27: 242-250.

Internet Links for Diopside

Specimens:
The following Diopside specimens are currently listed for sale on minfind.com.

Localities for Diopside

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
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