feldsparbearing

Feldsparbearing is a descriptive term used in geology to indicate that a rock or mineral sample contains feldspar minerals as a significant constituent. Feldspar refers to the two main groups of feldspar minerals: plagioclase (a series from albite to anorthite) and alkali feldspar (such as orthoclase, microcline, and sanidine). The phrase signals that feldspar is not merely present in trace amounts but contributes notably to the mineralogy and texture of the specimen.

In igneous rocks, feldsparbearing compositions span from felsic to intermediate types. Common examples include granites, granodiorites, rhyolites, and diorites with substantial feldspar in the groundmass or as phenocrysts. Arkosic or feldspathic sandstones also illustrate feldspar-rich sedimentary contexts. In metamorphic terranes, feldsparbearing rocks such as granulites or orthogneisses retain feldspar in their mineral assemblages, often reflecting the original crustal composition and metamorphic history.

Identification and analysis: feldsparbearing rocks are typically identified by the presence of visibly recognizable feldspar crystals or a feldspar-rich groundmass. In thin section, plagioclase shows characteristic twinning, while alkali feldspar may exhibit perthitic textures. X-ray diffraction or electron microprobe analysis can quantify feldspar content and distinguish feldspar types.

Significance: the feldspar content influences texture, geochemical interpretation, and weathering behavior, since feldspar alters to clay minerals during weathering. The term feldsparbearing serves as a concise descriptor in petrographic descriptions and rock classification discussions.