Cumberland Habit Quartz- Dalnegorsk, Primorsky Krai, Russia

Cumberland Habit Quartz
Dalnegorsk, Primorsky Krai, Russia
Dimensions: 8.4 x 6.4 x 3.4 cm

An unusual Quartz specimen from Dalnegorsk, Russia, featuring distinctive short, stout crystals with the pseudo-dipyramidal form known as the Cumberland habit. The crystals range from transparent to translucent colorless and pale smoky tones, with broad termination faces, extremely reduced prism faces, and complex intergrown formations creating a highly sculptural appearance.

Cumberland-habit Quartz develops when the rhombohedral faces become strongly dominant while the prism faces are greatly reduced or nearly absent. This produces crystals that can appear almost like two pyramids joined together. Dalnegorsk is a well-documented locality for this unusual Quartz habit, including specimens associated with the district's famous polymetallic deposits.

Specimens of this type are frequently labeled and sold as “Beta Quartz,” including material from Dalnegorsk, but the name is not technically correct for Cumberland-habit crystals. True β-quartz is the high-temperature form of SiO₂, stable at atmospheric pressure above approximately 573°C; on cooling, its structure converts to ordinary α-quartz. Cumberland-habit crystals are alpha, or low-temperature, Quartz whose unusual morphology simply resembles the classic bipyramidal appearance associated with β-quartz.