June 2022 – Coelestine

The mineral of the month June is coelestine, which belongs to the group of sulphates. In its pure form, coelestine is colourless and transparent. However, it often shows a bluish colour, which is caused by defects in the crystal lattice (so-called colour centres). If you heat it to over 200 °C, these defects heal and it loses its colour. Quite interesting, isn’t it?

Sr[SO₄]

Locality: Madagascar

Size: 4x10x5 cm (HxLxW)

Weight: 500 g