diamond

1.
a. a colourless exceptionally hard mineral (but often tinted yellow, orange, blue, brown, or black by impurities), found in certain igneous rocks (esp the kimberlites of South Africa). It is used as a gemstone, as an abrasive, and on the working edges of cutting tools. Composition: carbon. Formula: C. Crystal structure: cubic
b. (as modifier): a diamond ring
2. Geometry
a. a figure having four sides of equal length forming two acute angles and two obtuse angles; rhombus
b. rhombic
3.
a. a red lozenge-shaped symbol on a playing card
b. a card with one or more of these symbols or (when plural) the suit of cards so marked
4. Baseball
a. the whole playing field
b. the square formed by the four bases
5. black diamond a figurative name for coal
6. rough diamond an unpolished diamond
www.adiamondisforever.com
www.amnh.org/exhibitions/diamonds
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005