Ruby

A ruby is a pink to blood-red coloured gemstone, a variety of the mineral corundum. Other varieties of gem-quality corundum are called sapphires. Ruby is one of the traditional... Wikipedia

  • Category:  Oxide mineral variety
  • Formula, (repeating unit):  aluminium oxide with chromium, Al 2O 3:Cr
  • Crystal system:  Trigonal
  • Crystal class:  Hexagonal scalenohedral (3m), H-M symbol: (3 2/m)
  • Space group:  R 3c
  • Colour:  Orangy red through strongly purplish red.
  • Crystal habit:  Terminated tabular hexagonal prisms
  • Cleavage:  No true cleavage
  • Fracture:  Conchoidal, splintery
  • Tenacity:  Brittle
  • Mohs scale hardness:  9.0
  • Luster:  Subadamantine, vitreous, pearly (on partings)
  • Streak:  White
  • Diaphaneity:  Transparent, translucent
  • Specific gravity:  3.97–4.05
  • Optical properties:  Uniaxial/−
  • Refractive index:  n ω
  • Birefringence:  0.008 to 0.010
  • Pleochroism:  Strong: purplish-red – orangy-red
  • Dispersion:  0.018
  • Ultraviolet fluorescence:  Red under longwave
  • Common impurities:  Cr. (sometimes:Ti, Fe)
  • Data source:  DuckDuckGo