Sapphire | Gemopedia

September's birthstone has come a long way since the days when any and every blue stone was called a sapphire. Though its fame is shared with its "Big Three" counterparts ruby and emerald, sapphire has enjoyed a long run as one of the world's most beloved gemstones, earning itself a place of honor in crown jewels, royal accessories, museums, and even in modern royal engagement rings. Lest sapphire get too haughty, it has common uses as well. The rough polishing material on emery boards is made up of lower-quality corundum grains, strengthened with hematite, magnetite and quartz.
Colors
Blue, Strongly Greenish Blue, Violet Blue

Sapphire Classification

Common Name

Sapphire

Species

Corundum

Variety

Sapphire

Colors

Blue, Strongly Greenish Blue, Violet Blue

Alternate Names

Gemstone Groups

Key Separations

refractive index, birefringence, pleochroism, magnification and spectrum. The observation of natural internal characteristics is a key element in distinguishing natural sapphire from its synthetic counterparts.

Comments

Sapphire Optical Properties

Transparency

Transparent - Opaque

Refractive Index

1.762-1.77
Tolerance:(+0.009/-0.005)

Birefringence

0.008-0.01

Optic Character

Uniaxial

Optic Sign

Negative

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Inert to weak chalky blue or yellowish green
LWUV: Inert to weak red to orange

CCF Reaction

Pleochroism

Dichroic, moderate to strong, varying shades of body color

Dispersion

Strength: moderate fire Value: 0.018

Comments

Sapphire Chemistry & Crystallography

Chemical Name

aluminum oxide

Chemical Formula

Al2O3

Synthesis

Crystal System

Trigonal

Classification

Oxide

Nature

Natural

Crystallinity

Crystalline

Comments

Sapphire Characteristic Physical Properties

Hardness

9

Streak

White

Specific Gravity

3.95-4.1 Range:0.1/-0.05 Typical:4

Toughness

Good

Inclusions

Sapphire has type II clarity. Sometimes have silk, rutile, boehmite, apatite, calcite or zircon crystals. Fingerprint and negative crystal inclusions. Hexagonal growth and color zoning. Untreated stones will usually have inclusions intact. Heat treated stones will have fracture halos, discoid fractures or snowballs around crystal inclusions (untreated stones from magmatic areas might also show these characteristics). Silk will be broken and might show sintered areas especially around the girdle.

Luster

Bright Vitreous

Stability

Very Good

Fracture

Conchoidal

Cleavage

None

Comments

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