Feldspar is derived from German "Feld"- field and "Spath" - a rock that does not contain ore. There are two main subgroups that produce gems: the potassium feldspars and the plagioclases (a series from calcium to sodium feldspars).
- Albite - Sodium-rich Feldspar.
- Andesine - A plagioclase feldspar with an Albite: Anorthite molar ratio ranging from 50:50 to 70:30.
- Anorthite - Calcium-rich Feldspar.
- Bytownite - A plagioclase Feldspar with an Albite: Anorthite molar ratio ranging from 10:90 to 30:70.
- Labradorite - A plagioclase Feldspar with an Albite: Anorthite molar ratio ranging from 30:70 to 50:50.
- Spectrolite - Trade name for a Labradorite from Finland that shows the spectral colours especially effectively.
- Microcline - A triclinic Potassium Feldspar.
- Amazonite - A green to blue-green variety of Microcline.
- Oligoclase - A plagioclase feldspar with an Albite: Anorthite molar ratio ranging from 90:10 to 70:30.
- Orthoclase - A monoclinic Potassium Feldspar.
- Adularia - A gemmy colourless variety of Orthoclase.
- Moonstone - A variety of Orthoclase that exhibits a strong blue adularescence.
- Sanidine - A triclinic Potassium Feldspar found in lavas.
- Sunstone - A Plagioclase Feldspar, which exhibits aventurescence when viewed from certain directions.