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Augite

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Formula:
(Ca,Na)(Mg,Fe
2+
 
,Al,Fe
3+
 
,Ti)[(Si,Al)
 
2
O
 
6
]
System:MonoclinicColour:Brown-green, black, ...
Lustre:Vitreous, Resinous, DullHardness:5½ - 6
Member of:Clinopyroxene Subgroup > Pyroxene Group
Name:
Named by Abraham G. Werner in 1792 from the Greek αυγή ("auge") for "shine" or "luster," in allusion to the appearance of its cleavage surfaces. The modern definition of augite is that it is relatively low in calcium with some disorder of occupancies of Fe2+ and Mg in both octahedral sites. Fe:Mg may vary from 0 to 1 by definition. Augites tend to have minor (up to 10 atomic percent) Na, Al, Ti, or Fe3+ substitution that also may be disordered in the M2 and M1 sites. The full Ca, ordered equivalent of augite is the diopside-hedenbergite series.


Pyroxene Group, Clinopyroxene Subgroup. In the Ca-Fe-Mg (diopside-hedenbergite-augite) quadrilateral, the ideal structural formula is M2M1[Si2O6], where M2 is a distorted octahedral site which preferentially accepts large cations such as alkaline earth/alkali atoms (Ca, but may accept transition metals) and where M1 is a smaller regular octahedral site preferentially accepting transition metals, etc. (most commonly Mg, Fe2+). The substitutions containing no changes in valence within M2 (2+), Mi (2+), and tetrahedral sites, T (4+), is the normal scheme. A variety of additional substitution schemes, which require coupling of substituents, have been identified in these pyroxenes. Often these substitutions result in a change of species designation when they are dominant. Substitution 1 has Na substitution in M2 and trivalent ions of Al, Fe, Cr, and Sc substituting in M1. Substitution 2 involves Na substitution in M2 and mixed valance transition metals such as [Fe2+0.5Ti4+0.5] substituting in M1. Substitution 3, also called Tschermak's Component, involves coupled M1 octahedral and tetrahedral substitutions, such as CaAl[AlSiO6] or CaTi3+[AlSiO6]. Substitution 4 is a variant of Substitution 2 and has dominant Ca in M2 with mixed valence substitution in M1 involving divalent and tetravalent Ti and Al substitution in tetrahedral sites (e.g. Ca[(Mg, Fe2+)0.5Ti4+0.5)][AlSiO6]. In highly substituted Ca-Fe-Mg pyroxenes, several substitutional schemes may be identified. Substitution schemes 2 and 4 have not yet yielded named mineral species.

Augite is not just a member of the diopside-hedenbergite series. Augite is generally, sub-calcic, compared with diopside-hedenbergite. Augite, as defined by Morimoto, et al. (1988) may have Fe>Mg or Mg>Fe without change in name. Because of the unique way augite has been defined (Morimoto, et al, 1988), there is the implication that in rare cases, a variety of anions may be dominant in various the various sites, including M2, M1, and T. These extreme compositions are rare in the large majority of augites. The augites with En80Fo20 or Fs80Fo20 could be thought of as slightly alkalic clinoenstatite-clinoferrosilite. However, detailed chemical analysis and even structural analysis should be obtained in order to properly classify these unusual compositions. Similarly, extensive substitution of Na, for example, as in scheme 1 (Morimoto, et al., 1988) could lead to aegirine-augite or aegirine compositions depending on the other elements involved.


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Classification of Augite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:8/F.01-90
Nickel-Strunz 10th (pending) edition ID:9.DA.15

9 : SILICATES (Germanates)
D : Inosilicates
A : Inosilicates with 2-periodic single chains, Si2O6; pyroxene family
Dana 8th edition ID:65.1.3a.3

65 : INOSILICATES Single-Width,Unbranched Chains,(W=1)
1 : Single-Width Unbranched Chains, W=1 with chains P=2
Hey's CIM Ref.:16.23.1

16 : Silicates Containing Aluminum and other Metals
23 : Aluminosilicates of Fe, Ca, and Mg
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Occurrences of Augite

Geological Setting:Major rock forming mineral in mafic igneous rocks, ultramafic rocks and some high grade metamorphic rocks.

Physical Properties of Augite

Lustre:Vitreous, Resinous, Dull
Diaphaneity (Transparency):Translucent, Opaque
Colour:Brown-green, black, green-black, brown, purplish brown
Streak:Greenish gray, light to dark brown
Hardness (Mohs):5½ - 6
Tenacity:Brittle
Cleavage:Distinct/Good
Good on {110}
Parting:on {100} and {010}
Fracture:Irregular/Uneven, Sub-Conchoidal
Density (measured):3.19 - 3.56 g/cm3
Density (calculated):3.31 g/cm3

Crystallography of Augite

Crystal System:Monoclinic
Class (H-M):2/m - Prismatic
Space Group:B2/b
Space Group Setting:C2/c
Cell Parameters:a = 9.699Å, b = 8.844Å, c = 5.272Å
β = 106.97°
Ratio:a:b:c = 1.097 : 1 : 0.596
Unit Cell Volume:V 432.53 ų (Calculated from Unit Cell)
Z:4
Morphology:Stubby prismatic crystals
Twinning:Simple or multiple on {100}, also on {001}
Comment:Axial setting is C1 2/c 1
Crystal Atlas:
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Augite no.24 - Goldschmidt (1913-1926)
Augite no.111 - Goldschmidt (1913-1926)

About Crystal Atlas

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. The 3d models and HTML5 code are kindly provided by www.smorf.nl.

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Transparency
Opaque | Translucent | Transparent

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X-Ray Powder Diffraction:
d-spacingIntensity
3.22 (70)
2.99 (100)
2.94 (60)
2.90 (30)
2.56 (40)
2.53 (30)
2.51 (50)
2.13 (30)
Comments:ICDD 41-1483 (titanian augite)

Optical Data of Augite

Type:Biaxial (+)
RI values: nα = 1.680 - 1.735 nβ = 1.684 - 1.741 nγ = 1.706 - 1.774
2V:Measured: 40° to 52°, Calculated: 48° to 68°
Birefringence:0.032
Maximum Birefringence:δ = 0.026 - 0.039

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:High
Dispersion:r > v weak to distinct
Optical Extinction:Z : c = 35°-48°
Pleochroism:Visible
Comments:X= pale green, pale brown, green, greenish yellow
Y= pale brown, pale yellow-green, violet
Z= pale green, grayish green, violet

Chemical Properties of Augite

Formula:
(Ca,Na)(Mg,Fe
2+
 
,Al,Fe
3+
 
,Ti)[(Si,Al)
 
2
O
 
6
]
Simplified for copy/paste:(Ca,Na)(Mg,Fe2+,Al,Fe3+,Ti)[(Si,Al)2O6]
Essential elements:Ca, Mg, O, Si
All elements listed in formula:Al, Ca, Fe, Mg, Na, O, Si, Ti
Common Impurities:Ti,Cr,Na,Mn,K

Relationship of Augite to other Species

Member of:Clinopyroxene Subgroup > Pyroxene Group
Other Members of Group:

- +
Aegirine
NaFe
3+
 
Si
 
2
O
 
6
Aegirine-augite
(Na,Ca)(Fe
3+
 
,Fe
2+
 
,Mg,Al)Si
 
2
O
 
6
Clinoenstatite
MgSiO
 
3
Clinoferrosilite
Fe
2+
 
SiO
 
3
Diopside
CaMgSi
 
2
O
 
6
Esseneite
CaFe
3+
 
[AlSiO
 
6
]
Grossmanite
CaTi
3+
 
AlSiO
 
6
Hedenbergite
CaFe
2+
 
Si
 
2
O
 
6
Jadeite
Na(Al,Fe
3+
 
)Si
 
2
O
 
6
Jervisite
(Na,Ca,Fe
2+
 
)(Sc,Mg,Fe
2+
 
)Si
 
2
O
 
6
Johannsenite
CaMn
2+
 
Si
 
2
O
 
6
Kanoite
Mn
2+
 
(Mg,Mn
2+
 
)Si
 
2
O
 
6
Kosmochlor
NaCrSi
 
2
O
 
6
Kushiroite
CaAl[AlSiO
 
6
]
Namansilite
NaMn
3+
 
Si
 
2
O
 
6
Natalyite
Na(V
3+
 
,Cr)Si
 
2
O
 
6
Omphacite
(Ca,Na)(Mg,Al)Si
 
2
O
 
6
Petedunnite
Ca(Zn,Mn
2+
 
,Mg,Fe
2+
 
)Si
 
2
O
 
6
Pigeonite
(Mg,Fe
2+
 
,Ca)(Mg,Fe
2+
 
)Si
 
2
O
 
6
Spodumene
LiAlSi
 
2
O
 
6
Related Minerals - Nickel-Strunz Grouping):

- +
9.DA.05Donpeacorite
(Mn
2+
 
,Mg)Mg[SiO
 
3
]
 
2
9.DA.05Enstatite
MgSiO
 
3
9.DA.05Ferrosilite
FeSiO
 
3
9.DA.10Clinoenstatite
MgSiO
 
3
9.DA.10Clinoferrosilite
Fe
2+
 
SiO
 
3
9.DA.10Kanoite
Mn
2+
 
(Mg,Mn
2+
 
)Si
 
2
O
 
6
9.DA.10Pigeonite
(Mg,Fe
2+
 
,Ca)(Mg,Fe
2+
 
)Si
 
2
O
 
6
9.DA.15Diopside
CaMgSi
 
2
O
 
6
9.DA.15Esseneite
CaFe
3+
 
[AlSiO
 
6
]
9.DA.15Hedenbergite
CaFe
2+
 
Si
 
2
O
 
6
9.DA.15Johannsenite
CaMn
2+
 
Si
 
2
O
 
6
9.DA.15Petedunnite
Ca(Zn,Mn
2+
 
,Mg,Fe
2+
 
)Si
 
2
O
 
6
9.DA.15Davisite
CaScAlSiO
 
6
9.DA.15Kushiroite
CaAl[AlSiO
 
6
]
9.DA.15Grossmanite
CaTi
3+
 
AlSiO
 
6
9.DA.20Aegirine-augite
(Na,Ca)(Fe
3+
 
,Fe
2+
 
,Mg,Al)Si
 
2
O
 
6
9.DA.20Omphacite
(Ca,Na)(Mg,Al)Si
 
2
O
 
6
9.DA.25Aegirine
NaFe
3+
 
Si
 
2
O
 
6
9.DA.25Jadeite
Na(Al,Fe
3+
 
)Si
 
2
O
 
6
9.DA.25Jervisite
(Na,Ca,Fe
2+
 
)(Sc,Mg,Fe
2+
 
)Si
 
2
O
 
6
9.DA.25Kosmochlor
NaCrSi
 
2
O
 
6
9.DA.25Namansilite
NaMn
3+
 
Si
 
2
O
 
6
9.DA.25Natalyite
Na(V
3+
 
,Cr)Si
 
2
O
 
6
9.DA.30Spodumene
LiAlSi
 
2
O
 
6
Related Minerals - Hey's Index Grouping:

- +
16.23.2Dorrite
Ca
 
4
(Mg
 
3
Fe
3+
9
)O
 
4
(Si
 
3
Al
 
8
Fe
3+
 
O
 
36
)
16.23.3Vesuvianite
(Ca,Na,☐)
 
19
(Al,Mg,Fe
3+
 
)
 
13
(☐,B,Al,Fe
3+
 
)
 
5
(Si
 
2
O
 
7
)
 
4
(SiO
 
4
)
 
10
(OH,F,O)
 
10
16.23.5Ferro-hornblende
☐{Ca
 
2
}{Fe
2+
4
Al}(AlSi
 
7
O
 
22
)(OH)
 
2
16.23.6Magnesio-hornblende
☐{Ca
 
2
}{Mg
 
4
Al}(AlSi
 
7
O
 
22
)(OH)
 
2
16.23.7Aerinite
(Ca
 
5.1
Na
 
0.5
)(Fe
3+
 
,Al,Fe
2+
 
,Mg)
 
4
(Al,Mg)
 
6
[HSi
 
12
O
 
36
(OH)
 
12
][(CO
 
3
)
 
1.2
(H
 
2
O)
 
12
]

Other Names for Augite

Synonyms:
BasaltineHedenbergite-ÅgirinViolatiteVolcanic ShorlVolcanite (of Delamétherie)
Other Languages:
Basque:Augita
Catalan:Augita
Croatian:Augit
Czech:Augit
Dutch:Augiet
Esperanto:Aŭgito
Finnish:Augiitti
French:Augite
German:Augit
Violatit
Hebrew:אוגיט
Hungarian:Augit
Italian:Augite
Japanese:普通輝石
Lithuanian:Augitas
Polish:Augit
Russian:Авгит
Serbian (Cyrillic Script):Аугит
Simplified Chinese:普通辉石
Spanish:Augita
Violatita
Swedish:Augit
Tajik (Cyrillic Script):Авгит
Ukrainian:Авгіт
Varieties:
AsteroiteFassaiteFerroaugiteJeffersoniteKorea-Augite
Soda-AugiteTitanian AugiteUrbanite

Other Information

Fluorescence in UV light:Not fluorescent
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 Augite

Reference List:

- +
Dana, E. S. (1892) Dana's Systerm of Mineralogy, 6th edition, New York, NY: 352-364.
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.
Robinson, P., Ross, M., Nord, G.L., Smyth, J.R., and Jaffe, H.W. (1977) Exsolution lamellae in augite and pigeonite: fossil indicators of lattice parameters at high temperature and pressure. American Mineralogist: 62: 857-873.
Phillips, W. R. and D. T. Griffin (1981) Optical Mineralogy: 196-198.
Morimoto, N., Fabries, J., Ferguson, A. K., Ginzburg, I. V., Ross, M., Seifert, F. A., Zussman, J., Aoki, K., and Gottardi, G. (1988) Nomenclature of Pyroxenes, American mineralogist, v. 73, p. 1123-1133.
Deer, Howie, and Zussmann (1997): 2A: 294-398.

Internet Links for Augite

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    Localities for Augite

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