THE MINERAL HEDENBERGITE

Chemistry: CaFeSi2 O6, Calcium Iron Silicate
Class: Silicates
Subclass: Inosilicates
Group: Pyroxenes
Uses: only as a mineral specimen.
Specimens

Hedenbergite is a rock forming mineral in several metamorphic rocks, especially contact metamorphic rocks and skarns. It is also found in some igneous rocks and ore bodies.

Hedenbergite is a part of an important solid solution series of the pyroxene group. The series includes the minerals diopside, CaMgSi2 O6, and augite, (Ca, Na)(Fe, Mg, Al)(Al, Si)2 O6. Hedenbergite is the iron rich end member of the series. The diopside-hedenbergite series is analogous to the amphiobole, tremolite- actinolite series.

Hedenbergite although usually darker than its gemstone cousin diopside, can still be a wonderful mineral specimen. Its dark green to black color can be stricking with the bright luster that is found on some specimens. While this is not an uncommon mineral, good crystals of hedenbergite are rare and specimens that show nice crystals, good color and luster are prized.

PHYSICAL CHARACTERISTICS:

Color is black, greenish black, dark green and dark brown.
Luster is vitreous to dull.
Transparency crystals are translucent to opaque.
Crystal System is monoclinic; 2/m
Crystal Habits include short prismatic (with a square cross section) and accicular, rarely fibrous crystals. Good crystals are rare, more commonly compact, granular, lamellar and massive.
Cleavage is perfect in two lengthwise directions at close to right angles and a basal parting direction is sometimes seen.
Fracture is uneven to conchoidal.
Hardness is 5 - 6
Specific Gravity is approximately 3.2 - 3.6 (above average)
Streak is white to pale green.
Associated Minerals are wollastonite, grossular, andradite, magnetite, actinolite, galena, rhodonite and calcite.
Notable Occurrences include Fresno Co., California and Franklin New Jersey, USA; Nordmark Sweden; Broken Hill, Australia and Elba and Tuscany, Italy and Kazakhstan.
Best Field Indicators are crystal habit, associations, color, fracture and cleavage.