Ruby (Corundum)
Source: Afghanistan, Burma (Myanmar), Madagascar, Sri Lanka,Tajikistan, Thailand
Birthstone: July
The name “Ruby” (Rubis French, Rubin German, Rubino Spanish or Italian) is Latin for ‘Red.’ The Fiery Red colour of Ruby was thought to be caused by an Inextinguishable Flame, Lit from within the stone. Rubies were celebrated in the Bible, and in ancient Sanskrit writings as being the most precious of all gemstones, and Ruby was also known as the “Stone of Kings.”
Some of the finest Rubies in the world are mined in Myanmar (Burma) and Thailand, but within Southeast Asia they are also found in Cambodia and Vietnam. Other significant sources for rubies outside of Southeast Asia include Kenya, Afghanistan (Jagdalek, Jagdalak, or Jagdalik), Madagascar, Pakistan, Sri Lanka, and Tanzania.
Rubies belong to the same Aluminium Oxide Mineral family (Corundum) as Sapphire, and are both the Hardest and Toughest Gems in the world after Diamond. They are formed by intense Heat and Pressure, deep within Limestone rich in Clay. The primary occurrence of Ruby is found within Metamorphic Rock and Volcanic Igneous Rock or Basalt, and secondarily alluvial deposits. Corundum becomes a Ruby when it has trace amounts of the Chromophore Chromic (III) Oxide (Chromium). It is this Allochromatic Colouration that gives Ruby its highly Saturated, Deep Red colour. When Iron and Titanium are the principle Chromophores in Corundum it becomes Sapphire. Ruby can display strong Pleochroism when viewing the specimen from different angles, causing the gem to appear as either a Deep Red, or a Yellowish-Red.
A naturally occurring Ruby crystal
Natural Ruby with inclusions
A cut pink Ruby
Identification
Color: Near colourless through pink to all shades of red to a deep crimson
Crystal habit: Terminated tabular hexagonal prisms
Cleavage: No true cleavage
Fracture: Conchoidal, splintery
Tenacity: Brittle
Mohs scale: hardness 9.0
Luster: Sub adamantine, vitreous, pearly (on partings)
Streak: White
Diaphaneity: Transparent, translucent
Specific gravity: 3.97–4.05
Opticalproperties: Uniaxial
Refractive index: nω=1.768–1.772 – nε=760–1.763
Birefringence: 0.008
Pleochroism Strong: purplish-red – orangy-red
Dispersion: 0.018
Ultraviolet fluorescence: Red under longwave