Boracite: Gemstone Information
Boracite is magnesium chloroborate Mg3B7O13Cl and may produce pale green ornamental specimens. While some crystals, though members of the orthorhombic system, are pseudocubic others can be referred to pseudote tragonal morphology. Boracite is very slowly soluble in water, has a hardness of 7–7.5 and an SG of 2.91–3.10. The RI is 1.662–1.658, 1.662–1.667 and 1.668–1.673 for the alpha, beta and gamma rays respectively with birefrin- gence 0.011, biaxial positive. The lustre is vitreous to adamantine and a very weak greenish fluorescence has been reported. Facetable boracite is found in the Stassfurt and Hannover areas of Germany.