Agate is a type of microcrystalline quartz that is characterised by its fine grain and vibrant colours. Agate is known for its banded appearance, with alternating layers of different colours and ...

The reactivity of Tennessee limestones is mainly caused by crypto/microcrystalline quartz, chert, and finely disseminated silica in carbonate and clay/mica matrices, and it can be reasonably evaluated ...

Black onyx is a type of chalcedony, which is a form of microcrystalline quartz. It is known for its smooth, glossy, and solid ...

Secondary silica consists of spherulitic and granular chalcedony, microcrystalline quartz, and syntaxial quartz overgrowths. Although sandstone in places shows intergranular pressure solution textures ...