Oellacherite

Where it forms, where it's found

metamorphic rocks

Fine-grained granular dolomite.

16recorded occurrences

Source · OpenStreetMap

Physical

Hardness: 1Talc
2Gypsum
3Calcite
4Fluorite
5Apatite
6Orthoclase
7Quartz
8Topaz
9Corundum
10Diamond
Transparency: Transparent
Streak: White
Tenacity: flexible
Cleavage: Perfect
(001)
Fracture: Micaceous
Density: 2.884 g/cm³

Crystallography

Type-locality form: White mica

Chemical composition

Constituent elements: Mass composition breakdown
Element Atoms At. mass g/mol Mass g/mol Mass share
8OOxygen Oxygen 12 15.999 191.988
48.20%
14SiSilicon Silicon 3 28.085 84.255
21.15%
13AlAluminium Aluminium 3 26.982 80.946
20.32%
19KPotassium Potassium 1 39.098 39.098
9.82%
1HHydrogen Hydrogen 2 1.008 2.016
0.51%
Total 398.303 100.00%
Mass share = atoms × atomic mass ÷ molar mass × 100
From Mindat formula

Mass composition breakdown
Element	Atoms	At. mass g/mol	Mass g/mol	Mass share
8OOxygen	Oxygen	12	15.999	191.988	48.20%
14SiSilicon	Silicon	3	28.085	84.255	21.15%
13AlAluminium	Aluminium	3	26.982	80.946	20.32%
19KPotassium	Potassium	1	39.098	39.098	9.82%
1HHydrogen	Hydrogen	2	1.008	2.016	0.51%
	Total	398.303	100.00%

Literature, links & citation

Citations

1862Oellacher, Josef (1862) Margarit, Kenngott's Übersicht der Resultate mineralogischer Forschungen in den Jahre 1860, p. 49.
1867Dana, James Dwight (1867) Crystallogenic and Crystallographic Contributions. IV. On a Connection Between Crystalline Form and Chemical Constitution, with Some Inferences Therefrom. - Supplement, American Journal of Science, 44, 252-2.
1867DesCloizeau, Alfred Lewis Oliver Legrand (1867) Note on the Optical Characters of Different Micaceous Minerals Called Margarite. American Journal of Science, 44, 283-284. (with footnote by James Dwight Dana renaming the mineral oellacherite).

Cite this entry

@misc{mineral2026,
  author    = {Mineral Index editorial board},
  title     = {Oellacherite — Mineral Index},
  year      = {2026},
  url       = {https://mineralindex.org/minerals/oellacherite-10596},
  note      = {Accessed 2026-05-11}
}