Dioptase crystallizes forming Emerald-green masses, prismatic crystals, and crystalline aggregates. The mineral was first reported in 1801 by R.J. Haüly and was named from the Greek words meaning "throught" and "to see", referring to the ability to see the internal cleavage planes via looking through the mineral. It is a relatively rare mineral and is found in only a few localities.
 
Chemical Composition : CuSiO3 · H2O
Hardness 2.5 - 3
 
The various crystallized forms of Calcite include masses, grains, stalactites, scalenohedrons (twelve-faced crystals, each face exhibiting three unequal sides), and rhombodedrons (six-faced crystals, each face the shape of a rhombus). It is, however, characterized by the rhombohedron crystallization.
 
Calcite is a citreous colouress or white and can become green, pink, peach, golden, orange, yellow, red, blue, grey, or black, etc., when other compounds blend with it during formation. 
 
Calcite, named for its chemistry, was first reported as "Kalkspate" by A.F. Cronstedt in 1758, as "Calc-Spar" by R. Jameson in 1804, and translated to "Calcite" by J.K. Freiesleben in 1836. The name was initially applied to crystals of Calcium Carbonate pseudomorphous after Celestine/Celestite and was subsequently applied to the more common mineral which had been known as Calcspar. 
 
The Chemical composition is: (Ca,Co)CO3
Hardness 2.5 - 3