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Johannsenite  
Current inventory:  0 gems
 

Johannsenite

  
Johannsenite is named after Albert Johannsen (1871-1962), Professor and petrologist, University of Chicago, Chicago, Illinois, USA.

Discovered in 1932;   IMA status: Valid (pre-IMA; Grandfathered)

 

Chemistry

 

 

Chemical Formula:

CaMn2+(Si2O6)

 

Calcium Manganese Silicate

Molecular Weight:

247.18 gm

Composition:

Calcium

16.21 %

Ca

22.69 %

CaO

 

Manganese

22.23 %

Mn

28.70 %

MnO

 

Silicon

22.72 %

Si

48.62 %

SiO2

 

Oxygen

38.84 %

O

 

 

 

 

100.00 %

 

100.00 %

= TOTAL OXIDE

 

 

Classification

   

   

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/F.01-70

Nickel-Strunz 10th Ed. ID:

9.DA.15

 

9 : SILICATES (Germanates)
D : Inosilicates
A : Inosilicates with 2-periodic single chains, Si
2O6; pyroxene family

Related to:

Pyroxene Group, Clinopyroxene Subgroup, Hedenbergite-Johannsenite Series, Diopside-Johannsenite Series

Varieties:

None

Synonyms:

None

 

 

Crystal Data

   

   

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

As prismatic crystals, to 10 cm. In columnar, radiating, and spherulitic aggregates of fibers and prisms.

Twinning:

Simple and lamellar twinning common on {100}

 

 

Physical Properties

   

 

Cleavage:

Good on {110}, (110) ^ (110) ~87; partings on {100}, {001}, and {010}

Fracture:

Uneven to Conchoidal

Tenacity:

Brittle

Moh's Hardness:

6.0

Density:

3.27 - 3.54 (g/cm3)

Luminescence:

None

Radioactivity:

Not Radioactive

 

 

Optical Properties

   

   

Color:

Blue-Green, Greenish, Gray, Clove-Brown, Colorless; Colorless in thin section.

Transparency:

Translucent to Opaque

Luster:

Vitreous

Refractive Index:

1.703 - 1.745  Biaxial ( + )

Birefringence:

0.0290

Dispersion:

Weak to Moderate; r < v or r > v

Pleochroism:

None

 

 

Occurances

   

   

Geological Setting:

In metasomatized limestones and manganiferous skarns; in quartz or calcite veins cutting rhyolite.

Common Associations:

Rhodonite, Manganese Oxides

Common Impurities:

Ti, Al, Fe, Mg, Na, K, C, P, H2O

Co-Type Localities:

Temperino Mine, Temperino, Campiglia Marittima, Livorno Province, Tuscany, Italy
Civillina Mt., Recoaro Terme, Vicenza Province, Veneto, Italy
Franklin Mine, Franklin, Franklin Mining District, Sussex Co., New Jersey, USA

Year Discovered:

1932

View mineral photos:

Johannsenite Mineral Photos and Locations

 

 

More Information

   

   

 

Mindat.org
Webmineral.com

 

 


Johannsenite is a rare silicate mineral that is a member of the Pyroxene Group of minerals. It is rarely available as faceted gems but is a very attractive gem with bluish-green color, relatively good hardness and vitreous luster. The best sources of the attractive bluish-green material are the
N'Chwaning Mine, in South Africa and Civillina Mt. in Italy.

Sources of Johannsenite include Tetela de Ocampo, Puebla, and Pachuca, Hidalgo, Mexico. In the USA, at Franklin, Sussex County, New Jersey; from the Bohemia district, Lane County, Oregon; at the Aravaipa district, Graham County, Arizona; and in the Empire Zinc County mine, Hanover, Grant County, New Mexico. From Civillina Mt., Recoaro Terme, Vicenza Province, Veneto, Italy. In the Akatani mine, Niigata Prefecture; the Nakatatsu mine, Fukui Prefecture; the Onagusa mine, Katsuyam, Okayama Prefecture; and elsewhere in Japan. In the N'Chwaning Mine, Kalahari Manganese Field, Northern Cape Province, South Africa. A number of other localities are known.
 

  
Johannsenite gems for sale:

We have not photographed our Johannsenite gems. Please check back soon.
 

 

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