
Chrysocolla

Chrysocolla has a cyan (blue-green) color and is a minor ore of copper. A 2006 study has produced evidence that chrysocolla may be a microscopic mixture of the copper hydroxide mineral spertiniite, amorphous silica and water.
Due to being somewhat more common than turquoise, its wide availability, and vivid, beautiful blue and blue-green colors, chrysocolla has been popular for use as a gemstone for carvings and ornamental use since antiquity. It is often used in silversmithing and goldsmithing in place of turquoise and is relatively easy to work and shape.
Chrysocolla exhibits a wide range of Mohs hardness ranging from 2 through 7, which is dependent on the amount of silica incorporated into the stone when it is forming. Generally, dark navy blue chrysocolla is too soft to be used in jewelry, while cyan, green, and blue-green chrysocolla can have a hardness approaching 6, similar to turquoise.
Locality
Congo

Streak
White to a blue-green color
Hardness
Formula
2-7
Cu2 − xAlx(H2Si2O5)(OH)4·nH2O
Habit
Massive, nodular, botryoidal