Ruby Physical Properties

Ruby Physical Properties loose sale price & Ruby Gemstone Information



    * Chemical composition:Al2O3, color is due to trace impurities of Cr, Fe and Ti. LI>Class: oxides

    * Crystal system: hexagonal-rhombohedral, bar3 2/m

    * Crystal habit: sapphire crystals are commonly prismatic while ruby crystals are more often tabular {0001}, terminated by basal pinacoids, pyramidal and rhombohedral faces may be partly or entirely absent. Sapphires often occur as tapering hexagonal pyramids with a barrel-shaped form. Basal planes often have parallel striations meeting at 120 degrees forming successive equilateral triangles. Prismatic faces often have deep horizontal striations. Also massive and coarse to fine granular.

    * Twinning: commonly with multiple lamellar twinning on rhombohedral planes, less commonly with simple contact twins.

    * Specific gravity: 3.98-4.10

    * Index of refraction: 1.757-1.778

    * Birefringence: weak, 0.007-0.010

    * Pleochroism: pronounced. Blue sapphire: violet blue/blue-green, green sapphire: strong green/yellow-green, orange sapphire: yellow-brown to orange/colorless, purple sapphire: violet/orange, yellow sapphire: yellow/pale yellow and ruby: purple-red/orange-red

    * Hardness: 9

    * Color: Ruby: pinkish red to red. Sapphire (all other colors): blue, pink, green, yellow, violet, purple, orange, brown, white, gray, black and colorless. Some sapphire crystals are color zoned concentrically and/or along the C axis.

    * Luster: adamantine to vitreous, can occur with minute rutile inclusions oriented at an angle of 120 degrees from each other according to the hexagonal symmetry of the corundum. When this material is fashioned into a cabochon gem with the c axis of the corundum perpendicular to the base of the stone, reflected light from the rutile inclusions can concentrate on the surface of the gem forming white lines that intersect every 60 degrees forming a six ray star. This material is known as star ruby if it is pinkish-red to red, or as star sapphire with a color prefix for all other colors except blue which is simply called star sapphire.

    * Transparency: transparent to translucent

    * Cleavage: none - however, well developed parting on basal & rhombohedral planes is common.

    * Fracture: conchoidal, brittle

    * Streak: white




ENHANCEMENTS Heat treated. Common. Fractures filled, occasional.