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Johannsenite  
Current inventory:  0 gems
 

  
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, Si₂O₆; 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.
 

  
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