Sapphire is the gem quality
form of Corundum. It is second only to Diamond in hardness. The
hardness of corundum is due in part to the strong and short
oxygen-aluminium bonds. These bonds pull the oxygen and
aluminium atoms close together. This makes the crystal not only
hard but also quite dense for a mineral made up of two
relatively light elements.
Chemical Formula: Al2O3, Aluminium Oxide
VARIETY OF: Corundum , Al2O3 .
USES: Gemstone (for high grade material) and abrasive
blue, green, parti (a mix of colours), yellow, bi-coloured
Golden Yellow, orange, apricot, purple, pink, red (Ruby)
The pink to red colour of ruby stems from its chromium content,
whereas the sapphire's blue results from its titanium content.
Yellow and green sapphires contain variable amounts of ferrous
and ferric iron.
INDEX OF REFRACTION:
1.76 - 1.78
Lustre is vitreous to adamantine.
Transparency: Crystals are transparent to translucent.
Crystal System is trigonal; bar 3 2/m
Crystal Habits include sapphire's typical six-sided
barrel shape that may taper into a pyramid, and ruby's hexagonal
prisms and blades.
Specific Gravity is approximately 4.0+
Cleavage is absent, although there is parting which
occurs in three directions.
Streak is white.
Other Characteristics: Refractive index is around 1.77;
pleochroic (meaning colour intensity is variable from different
viewing directions); striations on parting surfaces
genuine sapphire -
made by nature
Resource on the Australian Sapphire Industry