Feldslaten

Feldslaten is a geological term that appears in limited scholarly contexts to describe a foliate metamorphic rock resembling slate but with a higher feldspar content. The name is derived from Dutch roots, with veld meaning field and slaten related to slate, and it has been used in regional or historical literature to distinguish a feldspar-rich variant of slate from more typical forms.

In terms of characteristics, feldslaten is described as a fine-grained, well-cleaved rock that can show a dull to pearly luster. It is often noted for laminae that reflect a higher proportion of feldspar minerals, such as plagioclase, compared with ordinary slate. The texture tends to be platy or layered, with a slaty cleavage that enables splitting along planes parallel to the foliation developed during metamorphism.

Formation and classification are somewhat ambiguous in modern geology. Feldslaten is generally considered to arise from low-grade regional metamorphism of feldspar-rich sedimentary rocks or volcanic ash, though the exact boundary between feldslaten and other feldspar-bearing slate varieties is not standardized. Because the term is not widely adopted in current classifications, some authors treat feldslaten as essentially synonymous with feldspathic slate or as a regional variant rather than as a distinct lithology.

Distribution and usage are limited to specific regional geological literatures, primarily from Europe and North America, with the term being far less common in contemporary practice. Modern references tend to prefer more precise descriptors such as feldspathic slate or slate with feldspar to avoid ambiguity.

See also: slate, schist, feldspathic rock. References to feldslaten are largely historical and regional, and researchers are advised to consult local glossaries or stratigraphic compilations for context.