2. Basic components: minerals

Radiolarians. Unicellular animals with a spherical shape. They have a marine origin. They are inherited.

Shells of molluscs or gastropods. They are recognised by their shape and internal fabric. They are of calcite or aragonite.

Bones. Mainly formed of apatite fibre (very low interference colour).

Crystals of different calcium salts. Some vegetable tissues can be observed. They can be of calcic carbonate or calcic oxalate (whevellite).

For all of them there is a description of their: shape, abundance, internal characteristics and alteration.