Homilite

Homilite
General
Category	Nesosilicate
Formula; (repeating unit)	Ca2(Fe2+,Mg)B2Si2O10
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
\|re\|er}}	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

Short description: Borosilicate mineral

Homilite is a borosilicate mineral belonging to the gadolinite group of minerals with formula Ca
2(Fe,Mg)B
2Si
2O
10.

It occurs as brown monoclinic crystals (space group P2₁/a^[5]) 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

↑ Mineral Society of America Handbook (PDF)
↑ Mindat with locations
↑ Webmineral data
↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine 85 (3): 291–320. doi:10.1180/mgm.2021.43. Bibcode: 2021MinM...85..291W.
↑ 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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[1] Mineral Society of America Handbook (PDF)

[2] Mindat with locations

[3] Webmineral data

[4] Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine 85 (3): 291–320. doi:10.1180/mgm.2021.43. Bibcode: 2021MinM...85..291W.

[5] 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.