The Collaborative International Dictionary of English v.0.48:

spar \spar\ (sp[aum]r), n. [AS. spaer in spaerst[=a]n
   chalkstone; akin to MHG. spar, G. sparkalk plaster.] (Min.)
   An old name for a nonmetallic mineral, usually cleavable and
   somewhat lustrous; as, calc spar, or calcite, fluor spar,
   etc. It was especially used in the case of the gangue
   minerals of a metalliferous vein.
   [1913 Webster]

   Blue spar, Cube spar, etc. See under Blue, Cube, etc.
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The Collaborative International Dictionary of English v.0.48:

Cube \Cube\ (k[=u]b), n. [F. cube, L. cubus, fr. Gr. ???? a
   cube, a cubical die.]
   1. (Geom.) A regular solid body, with six equal square sides.
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   2. (Math.) The product obtained by taking a number or
      quantity three times as a factor; as, 4x4=16, and 16x4=64,
      the cube of 4.
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   Cube ore (Min.), pharmacosiderite. It commonly crystallizes
      in cubes of a green color.

   Cube root. (Math.), the number or quantity which,
      multiplied into itself, and then into the product,
      produces the given cube; thus, 3 is the cube root of 27,
      for 3x3x3 = 27.

   Cube spar (Min.), anhydrite; anhydrous calcium sulphate.
      [1913 Webster]