Alspath
Alspath is a rare, colorless to white variety of adularia, a potassium feldspar mineral. Chemically, it is potassium aluminosilicate (KAlSi3O8). It is distinguished from other forms of adularia primarily by its appearance, often exhibiting a pearly or opalescent sheen. This sheen is a form of labradorescence, caused by the scattering of light from microscopic, regularly spaced lamellae (thin layers) within the mineral structure.
Alspath is typically found in hydrothermal veins and cavities in metamorphic and igneous rocks, often associated with other feldspar minerals, quartz, and zeolites. Geographically, occurrences are relatively limited, with notable finds reported in regions with significant alpine or volcanic activity.
Historically, Alspath has been used in jewelry making, although its rarity limits its widespread use. The opalescent effect makes it desirable for collectors and those seeking unique gemstones. While it lacks the hardness and durability of some other gemstones, it is sometimes cut into cabochons to showcase its internal reflections.
The name "Alspath" is derived from the Alps, where it was first discovered and described. The term "spath" is an old mineralogical term broadly referring to easily cleavable minerals.