földpátok

Földpátok are a group of rock-forming silicate minerals that make up roughly 41% of the Earth's continental crust. They are essential components of igneous, metamorphic, and sedimentary rocks. The name "földpát" comes from the Hungarian word for "earth" and "stone," reflecting their common occurrence.

These minerals share a common crystalline structure and chemistry. They are tectosilicates, meaning their structure is based on a three-dimensional framework of silica tetrahedra. The general chemical formula for földpátok is typically XY(Al,Si)4O8, where X and Y are cations such as potassium, sodium, or calcium.

The two main chemical groups of földpátok are the alkali földpátok and the plagioclase földpátok. Alkali földpátok have the general formula KAlSi3O8 (orthoclase and microcline) and NaAlSi3O8 (albite). Plagioclase földpátok form a solid solution series between albite (NaAlSi3O8) and anorthite (CaAl2Si2O8).

Földpátok are typically white, grey, or pink, though they can exhibit other colors depending on impurities. They have a Mohs hardness of 6 to 6.5 and a specific gravity of about 2.5 to 2.8. They exhibit two cleavage directions at nearly right angles.

Their abundance and widespread distribution make földpátok significant in geology and industry. They are used in the manufacturing of glass, ceramics, and as decorative stones.