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Sapphire  (variety of Corundum)
Current inventory:  0 gems
 

Chemistry:  Al₂O₃ + Fe,Ti,Cr  [Aluminum Oxide]

Discovered in Prehistory;   IMA status: Corundum is Valid (pre-IMA; Grandfathered).
The name Corundum is from the Sanskrit word kurivinda, possibly meaning Ruby. The name Sapphire is from the Latin word meaning blue.

Classification

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/C.04-10

Nickel-Strunz 10th Ed. ID:

4.CB.05

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
C : Metal: Oxygen = 2: 3,3: 5, and similar
B : With medium-sized cations

Related to:

Hematite Group. The aluminum analogue of Eskolaite, Hematite, and Karelianite. The red (Cr-bearing) gem variety is called Ruby.

Crystal Data

Crystallography:

Trigonal - Hexagonal Scalenohedral

Crystal Habit:

Crystals hexagonal, prismatic or steeply dipyramidal, tabular, rhombohedral, rarely acicular, typically rough, to 1 m; sectorially striated on [0001] k [1011]. Also granular, massive.

Twinning:

Common lamellar k [1011], may be an exsolution phenomenon. Contact or penetration twins on [0001] or [1011], rare.

Physical Properties

Cleavage:

None; Partings on [0001] and [1011]

Fracture:

Irregular/Uneven, Conchoidal

Tenacity:

Brittle

Hardness (Mohs):

9.0

Density:

3.99 - 4.10 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colorless, Gray, Brown, Pink, Orange, Yellow, Green, Blue to Cornflower Blue, Violet; may be color zoned, asteriated

Transparency:

Transparent to Translucent, Opaque

Luster:

Adamantine to Vitreous, Pearly on partings

Refractive Index:

1.760 - 1.772  Uniaxial ( - ); commonly anomalously Biaxial

Birefringence:

0.008 - 0.009

Dispersion:

0.018  (low)

Pleochroism:

Weak; e = blue-green to yellow-green, o = pale to deep blue

Other:

Asterism often present due to oriented needle-like inclusions or to colloidal or other material deposited in oriented tubules.

Occurances

Geological Setting:

Characteristic of Al-rich, Si-poor geological environments; in syenite and monzonite, and some quartz-free pegmatites; primary or a reaction product in eclogitic xenoliths in kimberlites. In regional or contact, high-grade metamorphic aluminous rocks, and some advanced argillic and potassic hydrothermal alteration assemblages; detrital in placers.

Common Associations:

Andesine, Oligoclase, Nepheline, Scapolite (syenites); Spinel, Rutile, chondrodite, “Hornblende”, Phlogopite, Calcite (metamorphosed limestones); Kyanite, Sillimanite, Dumortierite, Chlorite (schists); Pyrope-rich Garnet, Spinel, Phlogopite, Omphacitic Clinopyroxene, Kyanite, Rutile, Graphite, Diamond (eclogitic xenoliths).

Common Impurities:

Cr, Fe, V, Ti

Type Locality:

None; Prehistoric

Year Discovered:

Prehistoric

View mineral photos:

Sapphire Mineral Photos and Locations

More Information

Mindat.org (Sapphire)
Mindat.org (Corundum)
Webmineral.com (Corundum)

Sapphire is one of the top four in popularity of gems; Diamond, Sapphire, Ruby and Emerald. This is mostly due to its beauty, variety of colors and toughness as a jewelry gem. It is typically thought of as being a blue gem, but it is available in many other colors including blue-green, green, violet, purple, orange, yellow, golden, peachy pink, pink, colorless, and black. Ruby is the red or pinkish red variety of Corundum. With a Moh's hardness of 9.0 and no cleavage, it is a very durable gem for jewelry.

Sapphire is available from many locations around the world. Some of these locations, like Cambodia, Ceylon and Kashmir, are well known for their fine Sapphires.
 

  
Sapphire gems for sale:

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