Is an Hydrated Zinc Silicate Hydroxide with formula Zn4 Si2 O7 (OH)2 -H2O and hardness 5. In the past it was known as Calamina, but now this name is no longer in use. It occur in several colors such as yellow, brown,white, colorless and green or blue green. The most popular and attractive is the blue hemimorphite, recently China produced good sample of this mineral. This color is due to copper traces,sometimes associated with iron.