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Oellacherite

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Formula:
KAl2(AlSi3O10)(OH)2
Colour:
White, light gray white, pale lime green, green
Lustre:
Sub-Vitreous, Pearly
Hardness:
2 - 2½
Specific Gravity:
2.884 - 2.994
Name:
Re-named in 1867 by James Dwight Dana in honor of Josef Oellacher [February 16, 1804 Pressburg, Austria - August 16, 1880 Innsbruck, Austria], a chemical pharmacist who first investigated a similar mineral (Oellacher, 1862) and who thought it was margarite. The original oellacherite was from Kemmat, Sterzing (Vipiteno), Vizze Valley (Pfitsch Valley), Bolzano Province (South Tyrol), Trentino-Alto Adige, Italy. Because true margarite was discovered near Mt. Grenier, about 19 km distant from the oellacherite locality, there was some confusion that the two micas might be equivalent. Oellacher's (1862) chemical analysis was clearly not representative of margarite in DesCloizeaux's (1867) reckoning, but it was unusual in its chemistry containing Ba, Na, Ca, etc. DesCloizeaux's specimens were sent to him by Karl Rammelsberg labeled "Baryt-glimmer" and their optic axes seemed to suggest the mica was muscovite. The chemical anomaly prompted Dana to re-name the species. In 1933, Lawson H. Bauer and Harry Berman studied "oellacherite" from Franklin, New Jersey, USA, and re-named it, "barium muscovite", for its chemical relationship to muscovite, but the mineral from Franklin, New Jersey, USA was not Ba-dominant, either, although it too had anomalous chemical and physical properties.
A variety of Muscovite

A green to colorless, Ba-bearing variety of muscovite intermediate in chemical composition between true mica and brittle mica.


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Physical Properties of OellacheriteHide

Sub-Vitreous, Pearly
Transparency:
Transparent
Colour:
White, light gray white, pale lime green, green
Streak:
White
Hardness:
2 - 2½ on Mohs scale
Tenacity:
Flexible
Cleavage:
Perfect
{001}
Fracture:
Micaceous
Density:
2.884 - 2.994 g/cm3 (Measured)    

Chemical Properties of OellacheriteHide

Formula:
KAl2(AlSi3O10)(OH)2

Common AssociatesHide

PyriteFeS2
RealgarAs4S4
RealgarAs4S4
Associated Minerals Based on Photo Data:
Muscovite2 photos of Oellacherite associated with Muscovite on mindat.org.

Other InformationHide

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for OellacheriteHide

Reference List:
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Oellacher, Josef (1862) Margarit, Kenngott's Übersicht der Resultate mineralogischer Forschungen in den Jahre 1860, p. 49.
Dana, 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, volume 44, p. 252-2
DesCloizeau, Alfred Lewis Oliver Legrand (1867) Note on the Optical Characters of Different Micaceous Minerals Called Margarite, American Journal of Science, volume 44, p. 283-284. (with footnote by James Dwight Dana renaming the mineral oellacherite).

Internet Links for OellacheriteHide

Mineral and/or Locality  
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