Spinel | Gemopedia

Naturally dazzling spinel has graced the pages of history and many royal crowns due to its resemblance to ruby. Today, however, spinel stands on its own as a remarkable gem. Spinel comes in a wide range of stunning hues and can also exhibit optical phenomena like asterism and color-change. It is generally underappreciated compared to other colored stones, lending itself to more affordable prices, but this gem, said in Burma to be polished by the spirits, has a beauty that is difficult to ignore.
Alternate Names
Flame Spinel, Rubicelle, Ceylonite, Pleonaste
Colors
Red, Pink, Bluish Violet To Greenish Blue, Purple, Lavender, Blue, Bluish-Green, Brown, Black, Colorless, Green, Orange, Yellow

Spinel Classification

Common Name

Spinel

Species

Spinel

Variety

Colors

Red, Pink, Bluish Violet To Greenish Blue, Purple, Lavender, Blue, Bluish-Green, Brown, Black, Colorless, Green, Orange, Yellow

Alternate Names

Flame Spinel, Rubicelle, Ceylonite, Pleonaste

Gemstone Groups

Key Separations

refractive index, SR nature, magnification and spectrum. An accurate RI reading can distinguish natural from synthetic spinel, which usually has a higher RI. Red spinel often shows a chromium spectrum with lines in the red, possibly as emission lines.

Comments

Spinel frequently occurs in an octahedral form with triangular etch pits on the faces. Also appears in a flat twinned form as a macle. Flame spinel or rubicelle: orange, orange-red to yellowish red spinel usually from Brazilceylonite: dingy blue, gray to black with no iron contentpleonaste: opaque very dark blue or green to black containing iron. Misnomers: Balas ruby, spinel ruby, almandine spinel, sapphire spinel, sapphirine. Blue and red spinel tends to be on the higher side of the RI limit.

Spinel Optical Properties

Transparency

Transparent - Opaque

Refractive Index

1.718

Birefringence

0-0

Optic Character

NA

Optic Sign

NA

Polariscope Reaction

Singly Refractive (SR) With ADR

Fluorescence

SWUV: Variable
LWUV: Variable

CCF Reaction

Pink to red: inert to fluorescent red. Rare blue with cobalt: reddish inert if iron type

Pleochroism

Dispersion

Strength: moderate fire Value: 0.02

Comments

Spinel Chemistry & Crystallography

Chemical Name

magnesium aluminum oxide

Chemical Formula

MgAl2O4

Synthesis

Crystal System

Cubic

Classification

Oxide

Nature

Natural

Crystallinity

Crystalline

Comments

Spinel Characteristic Physical Properties

Hardness

8

Streak

Specific Gravity

3.57-3.7 Range:0.1/-0.03 Typical:3.6

Toughness

Varies

Inclusions

Spinel is a type II clarity stone. Stones might contain natural mineral inclusions like spinel or apatite, needles, negative crystals in the shape of an octahedral, fingerprints and iron oxide staining.

Luster

SubAdamantine

Stability

Very Good

Fracture

Conchoidal

Cleavage

None

Comments

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