Turquoise Chalk

Turquoise

Turquoise is an opaque, blue-to-green mineral that is a hydrous phosphate of copper and aluminium, with the chemical formula CuAl6(PO4)4(OH)8·4H2O. It is rare and valuable in finer grades and has been prized as a gemstone for millennia due to its hue.

Chalk

Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed under the sea by the accumulation and lithification of hard parts of organisms, mostly microscopic plankton, which had settled to the sea floor. Chalk is common throughout Western Europe, where deposits underlie parts of France, and steep cliffs are often seen where they meet the sea in places such as the Dover cliffs on the Kent coast of the English Channel.

Turquoise (color)

Turquoise is a cyan color, based on the mineral of the same name.

turquoise

Noun

1. A sky-blue, greenish-blue, or greenish-gray semi-precious gemstone.
2. A pale greenish-blue colour, like that of the gemstone.

Adjective

1. Made of turquoise (the gemstone).
2. Having a pale greenish-blue colour.

chalk

Noun

1. A soft, white, powdery limestone (calcium carbonate, CaCO3).
2. A piece of chalk, or nowadays processed compressed gypsum (calcium sulfate, CaSO4), that is used for drawing and for writing on a blackboard (chalkboard).

Verb

1. To apply chalk to anything, such as the tip of a billiard cue.
2. To record something, as on a blackboard, using chalk.