Rhodonite

rhodonite (ROE-duh-nite) is a mineral species; triclinic crystal system;chemical composition (Mn, Fe, Mg, Ca)SiO3
usually translucent to opaque pink to brownish or purplish red, often with black veins or splotches (may also have greenish or yellowish areas due to impurities); also transparent pink to red (rare)

Identification

Optic Character: DR, biaxial positive; AGG
Refractive Index: 1.733-1.747 (+.010, -.013); spot reading usually 1.73, but may be 1.54 due to quartz impurities
Birefringence: .010 to .014
Pleochroism: none in aggregate material; transparent crystals – weak to moderate, orange-red and brownish red
Ultraviolet Fluorescence: inert
Absorption Spectra: broad band centered around 545 nm and a line at 503 nm
Cause of Color: manganese
Specific Gravity: 3.50 (+.26, -.20)
Polish Luster: vitreous to subvitreous
Fracture: conchoidal to uneven or granular
Luster: dull to vitreous
Cleavage: perfect in two directions but usually obscured by aggregate structure
Identifying Characteristics: black veins or spots of manganese oxide
Crystal Habit: usually massive
Hardness: 5 1/2 to 6 1/2
Toughness: good (aggregates) to poor (transparent stones)

Sources: Australia, Brazil, Germany, Italy, Mexico, Romania, Sweden, US, USSR

Gem Reference Guide, Published by GIA. ISBN 0-87311-019-6

Gemstones of the World, Published by Sterling Publishing Co., Inc NY, ISBN 1-4027-4016-6

Encyclopedia of GEMSTONE, Published by ISHINSHA CO., LTD. ISBN 978-986-251-831-1