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Ruby  (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, through the Tamil word kurundam. The name Ruby is from the Latin word meaning red.

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:

Red to Pinkish Red; 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 to None

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:

Ruby Mineral Photos and Locations

More Information

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

Ruby is the red to pinkish red variety of the Corundum mineral group that also includes Sapphire which is known primarily as the blue variety although it is available in many colors. Ruby is one of the top four gems (Diamond, Sapphire, Ruby and Emerald) in popularity. This is mostly due to its beauty, intense color and toughness in jewelry. With a Moh's hardness of 9.0 and no cleavage, it is a very durable gem for jewelry. Ruby's red color is caused by minor amounts of trivalent Chromium (Cr) replacing Aluminum (Al) in the crystal structure. Pure Cr₂O₃ occurs in nature as the mineral Eskolaite, which is green.

Ruby is available from many locations around the world. Some of these locations such as Burma, Ceylon and Madagascar, are well known for their fine Rubies.
 

  
Ruby gems for sale:

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