Quantcast

The Mineral johannsenite

Olive-Green Johansennite

Johannsenite is a rare member of the pyroxene group that is isomorphous with Diopside and Hedenbergite. It often occurs with black manganese oxide dendrites on its surface. Johannsenite alters to become the pink mineral Rhodonite. Johannsenite is named in honor of Albert Johannsen (1871-1962), a petrologist and professor at the University of Chicago.

Chemical Formula

CaMnSi2O6

Color

Gray, brownish-gray, greenish-gray, olive-green, light blue, cream yellow. May also be banded.

Crystal System

Monoclinic

Properties

Streak
White
Hardness
5 - 6
Transparency
Translucent to nearly opaque
Specific Gravity
3.4 - 3.6
Luster
Vitreous to greasy
Cleavage
1,2 - prismatic at cleavage angles of 87º and 93º (Characteristic of minerals in the pyroxene group). May also exhibit parting in one direction.
Fracture
Uneven to splintery
Tenacity
Brittle

Crystal Habits

As elongated and stubby prismatic crystals, in thick tabular crystals, in radiating and fibrous aggregates, massive, and in rounded masses.

Additional Information

Composition
Calcium manganese silicate, sometimes with iron
In Group
Silicates; Inosilicates; Pyroxene Group
Striking Features
Crystal habits, localities, color, and cleavage habits
Environment
Manganese-rich deposits of contact metamorphic rocks.
Rock Type
Metamorphic

Noteworthy Localities

Johannsenite is found in slender acicular crystals and in banded masses at Monte Civillina, Recoaro, Italy; and in olive green crystals in the North Mine, Broken Hill, New South Wales, Australia. Brown crystals associated with Rhodochrosite come from the Uchucchaqua Mine, Oyon Province, Peru. In the U.S., the premier locality is the Iron Cap mine, Landsman Camp, Graham Co., Arizona. Other occurrences are Hanover, Grant County, New Mexico; and Franklin, Sussex Co., New Jersey.

Common Mineral Associations

Rhodonite, Bustamite, Pyrolusite, Sphalerite, Quartz, Calcite, Wollastonite

Distingushing Similar Minerals

The localities and crystal habits of this mineral can distinguish from most minerals.

johannsenite Photos



Close

Copyright © 2020. Minerals.net

View on Full Site