Lazurite, Kunar Province, Afghanistan.
Also known as lapis lazuri, this precious blue mineral has been valued for centuries as a pigment and gemstone.
Source: Museum Victoria
Corundum, Kapisa Province, Afghanistan.
Gem-quality red corundum is known as ruby when cut and polished.
Source: Museum Victoria
Limestone, which is mainly calcite derived from the shells of marine animals, is changed by metamorphism into coarse-grained marble. Any impurities of sand and clay in the limestone provide extra ingredients to form attractive gem minerals, such as corundum, spinel and lazurite.