External appearance of minerals – diversity of forms
Minerals are crystalline solids, most often formed by crystallisation from magma or hydrothermal solutions, and if they grow freely, they will develop into geometric polyhedrons with flat faces and a specific degree of symmetry that we call – CRYSTALS. These beautifully developed crystal shapes are usually found in cavities and voids within rocks. The outer shape of the crystal is a reflection of the internal organisation of its atoms, and as crystal grows, differences in temperature, pressure and the chemical composition of its environment cause fascinating variations.