tarjonsten

Tarjonsten is a fictional mineral frequently used in geology education and speculative fiction to illustrate mineralogical concepts. It is not recognized by major mineral nomenclature bodies and has no verified natural occurrence.

Etymology and scope: The name tarjonsten combines a fictional Tarjon region with the Norwegian word sten meaning stone, reflecting its typical use in Nordic teaching materials. As a teaching placeholder, tarjonsten appears in multiple, non–peer-reviewed sources with varying details.

Description and properties: Tarjonsten is described as a silicate mineral with a variable composition. In many depictions it crystallizes in a monoclinic system and occurs as prismatic crystals with a vitreous to pearly luster. Color ranges from pale green to gray. Reported hardness is usually around 5–6 on the Mohs scale, with a white or pale streak. Cleavage is described as imperfect or multi-directional in different sources.

Composition and solid solution: Because tarjonsten is fictional, reported empirical formulas differ. It is often described as an aluminosilicate with significant iron, magnesium, and aluminum content, allowing extensive chemical substitutions and a broad range of compositions in different depictions.

Occurrence and context: In educational scenarios, tarjonsten is said to form in pegmatites and hydrothermal veins and is sometimes placed in simulated field locations. It is commonly paired with minerals such as quartz, feldspar, biotite, and hornblende to demonstrate associations in teaching datasets.

Classification and use in teaching: Tarjonsten is used to illustrate mineral classification by crystal structure, chemical composition, and physical properties. It serves as a placeholder for exercises on identification, zoning, and solid-solution concepts without relying on a real mineral.

See also: Fictional minerals, Mineralogy education, Glossary of mineral terms. References: No peer-reviewed sources verify tarjonsten; it appears in textbooks and fiction as a teaching example.