Gahnospinel | Gemopedia

Gahnospinel is the rare violetish to dark blue, zinc-rich variety of spinel. A variety of spinel rich in zinc, much of the world's supply of gahnospinel comes from Sri Lanka. Since gahnospinel is chemically midway between spinel and gahnite, hence its name is a combination of the two. The first half is in honor of Johann Gottlieb Gahn, a Swedish chemist and mineralogist.
Colors
Green, Blue Dark In Tone, Very Dark Green, Brown To Black

Gahnospinel Classification

Common Name

Gahnospinel

Species

Gahnospinel

Variety

Colors

Green, Blue Dark In Tone, Very Dark Green, Brown To Black

Alternate Names

Gemstone Groups

Spinel

Key Separations

Dark color, RI, SR nature, spectrum and SG

Comments

Gahnospinel is rich in zinc and has properties in between spinel and gahnite.

Gahnospinel Optical Properties

Transparency

Transparent - Translucent

Refractive Index

1.76
Tolerance:(+0.020/-0.020)

Birefringence

Optic Character

NA

Optic Sign

Polariscope Reaction

Singly Refractive (SR)

Fluorescence

SWUV: Inert
LWUV: Inert

CCF Reaction

Pleochroism

None

Dispersion

Comments

Gahnospinel Chemistry & Crystallography

Chemical Name

magnesium zinc aluminum oxide

Chemical Formula

MgAl2O4 and ZnAl2O4

Synthesis

Crystal System

Cubic

Classification

Oxide

Nature

Natural

Crystallinity

Crystalline

Comments

Gahnospinel Characteristic Physical Properties

Hardness

7.5-8

Streak

White

Specific Gravity

3.61-4.41 Typical:4.01

Toughness

Good

Inclusions

Luster

Vitreous

Stability

Fracture

Conchoidal

Cleavage

None

Comments

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