Rockthat

Rockthat is a fictional rock type described in geology education and in science-fiction contexts to illustrate how new rock classifications are named and described. It is not a real mineral species or formally recognized rock unit.

Etymology and naming: The term combines “rock” with the demonstrative “that” to indicate its hypothetical status in teaching scenarios. It typically appears in case studies or problem sets to explore texture and mineralogy concepts, rather than in formal geologic nomenclature.

Description: In the standard educational model, rockthat is envisioned as a coarse-grained rock with a textured mosaic of light-colored feldspar and quartz grains, intergrown with mica. Small amounts of dark minerals such as amphibole or pyroxene may be present. The texture is often porphyritic, with larger phenocrysts set in a finer-grained groundmass, and the overall appearance can range from gray to pinkish hues depending on mineral content.

Formation and occurrence: As a teaching device, rockthat is said to form through metasomatic alteration or mixed crystallization environments in the crust, under moderate temperatures and pressures. No real-world occurrence is cited; it serves to illustrate how textures reflect formation conditions and mineral interactions.

Significance: The concept helps students understand rock classification, texture, mineralogy, and how geologists interpret formation histories. It is sometimes used in textbooks and classroom exercises to practice describing rocks and reasoning about their origins.

See also: metamorphic rock, igneous rock, rock classification.