Is a Hydrated Zinc Silicate Hydroxide with formula: Zn4 Si2 O7 (OH)2 -H2O .
The hardness is 4.5-5.
Well known among mineral collectors for the nice colour and botryoidal shapes.
The most popular material comes from China, like this stone.
Normally is not cut as a gemstone and rarely facetted.
The overall appearance is translucent with some clouds.