complete silicate of aluminum and boron, 1759, from French or German, ultimately from Sinhalese toramalli, a general name for cornelian.

(n) a mineral that is a complex borosilicate and hydroxide of aluminum containing iron and magnesium and calcium and lithium and sodium; it is usually black but occurs in transparent colored forms tha [..]

A semiprecious gemstone that is available in a wide range of colours, and that can appear to have more than one colour in itself. Tourmaline has a hardness of 7-7.5 on the Mohs Scale

Tourmaline is a fascinating mineral that can actually exhibit two or more colors in one crystal. Tourmaline possesses one of the widest color ranges, reproducing every conceivable color in a rainbow. On Mohs' scale of hardness, tourmaline is 7.5. It is vitreous on crystal surfaces and greasy on fractures. Sources of tourmaline include Brazil ( [..]

"Tourmaline is a crystal silicate mineral compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline gem stones come in a wide variety of colors. The name comes from the Sinhalese word ""turamali"" or ""toramalli"", which applied to different gemstones found in [..]

A crystal silicate mineral compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline gem stones come in a wide variety of colours. The name comes from the [..]

A complex black or dark coloured borosilicate mineral, compounded with various chemical elements and considered a semi-precious stone. * date=2012-03 |author=Lee A. Groat |title=Gemstones |volume=1 [..]