| Homilite | |
|---|---|
| General | |
| Category | Nesosilicate |
| Formula (repeating unit) | Ca2(Fe,Mg)B2Si2O10 |
| IMA symbol | Hom |
| Strunz classification | 8/B.29-30 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) |
| Space group | P21/b |
| Unit cell | a = 9.78 Å, b = 7.61 Å, c = 4.78 Å; β = 90.56°; Z = ? |
| Identification | |
| Color | Greenish to brownish black |
| Mohs scale hardness | 5–5+1⁄2 |
| Luster | Vitreous, resinous |
| Diaphaneity | Opaque |
| Specific gravity | 3.34 |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.715 nβ = 1.725 nγ = 1.738 |
| Birefringence | δ = |
| 2V angle | Measured: 80° |
| References | |
Homilite is a borosilicate mineral belonging to the gadolinite group of minerals with formula Ca2(Fe,Mg)B2Si2O10.
It occurs as brown monoclinic crystals (space group P21/a) within feldspar masses in pegmatite and was discovered in 1876 in Stoko island, Langesundfiord, Norway. The name is from the Greek for to occur together, in allusion to its association with meliphanite and allanite.
References
- Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- Mineral Society of America Handbook (PDF)
- Mindat with locations
- Webmineral data
- Miyawaki, R.; Nakai, I.; Nagashima, K. (15 January 1985). "Structure of homilite, Ca2.00(Fe0.90Mn0.03)B2.00Si2.00O9.86(OH)0.14". Acta Crystallographica Section C Crystal Structure Communications. 41 (1): 13–15. doi:10.1107/S010827018500261X.
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