Hoelite

Hoelite is a mineral, discovered in 1922 at Mt. Pyramide, Spitsbergen, Norway and named after Norwegian geologist Adolf Hoel (1879–1964). Its chemical formula is C₁₄H₈O₂ (9,10-anthraquinone).^[2]

Hoelite
Yellow acicular crystals of hoelite (picture size: 10 mm)
General
Category	Organic mineral
Formula (repeating unit)	C14H8O2
IMA symbol	Hoe[1]
Strunz classification	10.CA.15
Dana classification	50.4.2.1
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/a
Unit cell	a = 15.81 Å, b = 3.967 Å c = 7.876 Å; β = 102.67°; Z = 2
Identification
Color	Yellow, yellowish green
Crystal habit	Acicular clusters; pseudo-orthorhombic
Cleavage	Good
Streak	Light yellow
Diaphaneity	Semitransparent
Specific gravity	1.42
Optical properties	Biaxial (+)
Refractive index	nα≈1.75, nβ≈1.75, nγ≈2.0
References	[2][3]

It is a very rare organic mineral which occurs in coal fire environments in association with sal ammoniac and native sulfur.^[2]

References

1. 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.
2. Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (eds.). "Hoelite" (PDF). Handbook of Mineralogy. Chantilly, VA: Mineralogical Society of America. Archived from the original (PDF) on 4 March 2016. Retrieved 12 September 2017.
3. Barthelmy, Dave. "Hoelite". Mindat.org. Retrieved 12 September 2017.