Celestine

Celestine is formed of prismatic or tabular crystals and also commonly occurs in compact, radiating, fibrous, granular or nodular aggregates. Their colours range from colourless to milk-white, blue and yellowish brown. It is semi-hard and heavy and varies from transparent to translucent. Insoluble in acids, it is however slightly soluble in water. When heated, it melts easily, forming a milk-white globule.

It originates in hydrothermal veins, in sedimentary rocks (evaporites, limestones and dolomites), and is also present in magmatic rocks.

The main use of celestine is the extraction of strontium, used in the fireworks and tracer-bullet industry, in paints and for refining beet sugar.