Tephroite Value, Price, and Jewelry Information

Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons

Tephroite

Tephroite is generally reddish brown and barely translucent. However, it takes a good polish and is massive enough to make good cabochons. Only the New Jersey and Australian localities seem to have provided such material, however. Faceted gems are unknown.

Tephroite Information

Data Value
Name Tephroite
Is a Variety of Peridot
Formula Mn2SiO4.
Colors Reddish brown, salmony pink, blue-green, olive, green, gray.
Fracture Conchoidal, uneven
Hardness 6
Cleavage Distinct
Crystallography Orthorhombic; crystals prismatic, elongated; commonly massive, compact, as disseminated grains.
Refractive Index 1.770-1.825
Birefringence 0.037-0.047
Absorption Spectrum Not reported, but Mn lines should be observed.
Pleochroism Distinct: greenish blue/reddish/brownish red.
Optics a = 1.770-1.788; β = 1.807-1.810; γ = 1.817-1.825. Biaxial (-).
Optic Sign Biaxial -
Luster Vitreous to greasy.
Specific Gravity 4.11
Transparency Transparent to opaque.

Streak: pale gray.

Optics: a =1.770-1.788; β= 1.807-1.810; γ=1.817-1.825.

Biaxial (—).

Occurrence: In iron-manganese ore deposits and associated skarns.

California; Colorado.

Franklin and Sterling Hill, New Jersey: cuttable.

England; Sweden; France; Japan.

Tamworth. NS.W. Australia: small Mn deposits with massive tephroite streaks in rhodonite.

This material is suitable for cabochons.

Comments: Tephroite is generally reddish brown and barely translucent. However, it takes a good polish and is massive enough to make good cabochons. Only the New Jersey and Australian localities seem to have provided such material, however. Faceted gems are unknown.

Name: From the Greek tephros, meaning ash colored.

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