[1] : The Collaborative International Dictionary of English v.0.48

corundum \corun"dum\ k-oru^n"du^m, n.; pl. corundums
   k-oru^n"du^mz. also corindon. from hind. kurand
   corundum stone. min.
   the mineral alumina al2o3, as found native in a
   crystalline state. transparent varieties are used as
   gemstones, including sapphire, which is the fine blue
   variety; the oriental ruby, or red sapphire; the oriental
   amethyst, or purple sapphire; and adamantine spar, the
   hair-brown variety. it is the hardest substance found native,
   next to the diamond.
   1913 webster +pjc

   note: the name corundum is sometimes restricted to the
         non-transparent or coarser kinds. emery is a
         dark-colored granular variety, usually admixed with
         magnetic iron ore.
         1913 webster
see also:
corundums al2o3 sapphire oriental ruby oriental amethyst adamantine spar 
emery 

Adamantine >> A Words
Adamantine, definition of term: Adamantine
adamantine_pag1.html

Spar >> S Words
Spar, definition of term: Spar
spar_pag1.html

Bitter Spar >> B Words
Bitter Spar, definition of term: Bitter Spar
bitter+spar_pag1.html