Chrysocolla
Chrysocolla is a complex copper silicate. It has the most common bright cyan (blue-green) color and its hardness is 2.5 to 7.0. It is located in the oxidation zone of copper ores. Associated minerals are quartz, limonite, azurite, malachite, cuprit and other secondary copper minerals.
If it is lighter, it may be mistaken for turquoise.
Chrysocolla is very well machined and has been a popular raw material in jewelry since ancient times.