Any of a group of hard crystalline minerals that consist of aluminum silicates of potassium or sodium or calcium or barium WordNet 3.0 & Open English WordNet

Feldspar is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. Wikipedia

Group of rock-forming minerals including Wikipedia Disambiguation

Mineral group Wikidata

Any of a large group of rock-forming minerals that, together, make up about 60% of the earth's outer crust. The feldspars are all aluminum silicates of the alkali metals sodium, potassium, calcium and barium. Feldspars are the principal constituents of igneous and plutonic rocks. Wiktionary

Any of a large group of rock-forming minerals. Wiktionary (translation)