2. What is Corundum?
• Corundum is a crystalline form of aluminium
oxide (Al 2O 3) typically containing traces of
iron, titanium, vanadiumand chromium. It is a
rock-forming mineral. It is one of the naturally
transparent materials, but can have different
colors when impurities are present.
Transparent specimens are used as gems,
called ruby if red and padparadscha if pink-
orange. All other colors are called sapphire,
e.g., "green sapphire" for a green specimen.
3.
4. PhysicalPropertiesof Corundum
Chemical
Classification
oxide
Color
Typically gray to brown. Colorless when pure but trace amounts of various
metals produce almost any color. Chromium produces red (ruby) and
combinations of iron and titanium produce blue (sapphire).
Streak colorless (harder than the streak plate)
Luster adamantine to vitreous
Diaphaneity transparent to translucent
Cleavage None. Corundum does display parting perpendicular to the c-axis.
Mohs Hardness 9
Specific Gravity 3.9 to 4.1 (very high for a nonmetallic mineral)
Diagnostic Properties
hardness, high specific gravity, hexagonal crystals sometimes tapering to a
pyramid, parting, luster, conchoidal fracture
Chemical
Composition
Al2O3
Crystal System hexagonal
Uses
Historically used as an abrasive. Specimens with pleasing colors have a long
history of gemstone use.
5.
6. Group 9
•Lovely Lorelie D. Planos
Mary Antonette D. Picones
Jhea R. Francisco
Andrea Mae J. Del Rosario
Irish Saporna
Dawn Aubrey Espedillon
