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Tschermakite  
Current inventory:  0 gems
 

  
Tschermakite was named to honor Professor Gustav Tschermak von Seysenegg (1836-1927), Austrian mineralogist, University of Vienna, Vienna, Austria.

Discovered in 1945.   IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Ca₂Mg₃Al₃Fe³⁺Si₆O₂₂(OH)₂

Calcium Magnesium Aluminum Iron Silicate Hydroxide

Molecular Weight:

844.38 gm

Composition:

Calcium

9.49 %

Ca

13.28 %

CaO

Magnesium

8.64 %

Mg

14.32 %

MgO

Aluminum

9.59 %

Al

18.11 %

Al₂O₃

Iron

6.61 %

Fe

9.46 %

Fe₂O₃

Silicon

19.96 %

Si

42.69 %

SiO₂

Hydrogen

0.24 %

H

2.13 %

H₂O

Oxygen

45.48 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/F.10-60

Nickel-Strunz 10th Ed. ID:

9.DE.10

9 : SILICATES (Germanates)
D : Inosilicates
E : Inosilicates with 2-periodic double chains, Si₄O₁₁; Clinoamphiboles

Related to:

Amphibole Group. Calcic Clino-Amphibole Subgroup. Tschermakite - Ferrotschermakite Series.

Synonyms:

Tschermakitic hornblende, Aluminotschermakite

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

As prismatic crystals; as reaction rims on other minerals.

Twinning:

Simple or multiple twinning || {100}.

Physical Properties

Cleavage:

Perfect on {110}, intersecting at 56º and 124º; partings on {100}, {001}.

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

5.0 - 6.0

Density:

3.15 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Medium Green to dark Green to Green-Black to Black, Brown (rare).

Transparency:

Transparent to Opaque

Luster:

Vitreous

Refractive Index:

1.68 - 1.698  Biaxial ( + ) or ( - )

Birefringence:

0.0180

Dispersion:

Strong; r > v

Pleochroism:

Visible to Distinct; in greens and browns

Occurances

Geological Setting:

From eclogites and other ultramafic igneous rocks, and in medium- to high-grade metamorphic rocks, typically amphibolites.

Common Associations:

Kyanite, Garnet

Common Impurities:

Ti, Mn, Na, K, H₂O

Type Locality:

(possibly Bamle, Norway)

Year Discovered:

1945

View mineral photos:

Tschermakite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Tschermakite is a fairly common but rarely identified mineral. It often occurs in association with massive green Zoisite and Ruby at the Mundarara Mine,  Longido, Mt. Kilimanjaro, Kilimanjaro Region of Tanzania. Black inclusions of Tschermakite are frequently seen in attractive cabochons of bright green Zoisite and pinkish-red Ruby.

Probably widespread. Well-studied material from: Hurry Inlet, Fiskenæsset, Greenland. At Glenelg and Knockormal, Ayrshire, Scotland. From Lake Kutemajärvi, Orivesi, and Perniö, Finland. In France, from Le Viala du Tarn, Aveyron. From the central Bug region, Ukraine.
 

  
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