Se trata de excelente cristal de cuarzo que presenta crecimientos en "ventana" (también llamados "esqueletales") muy marcados en las deformadas caras romboédricas. Prisma muy poco desarrollado. Muy buena transparencia, tono ligeramente ahumado, y un brillo más que excepcional. Se observan inclusiones de tono beige muy habituales en este tipo de crecimientos. Estos ejemplares fueron recogidos cerca del embalse de Urrúnaga, en Legutio.

A very particular quartz crystal that shows a very marked "window" growths (also called "skeletal") in the rhombohedron faces and with a short prism. Very good glassy luster. With inclusions those are very common in this type of quartz crystals. These specimens were collected near the Urrúnaga reservoir in Legutio. Nowadays it is near impossible find these specimens.

Group of crystals, one of them clearly dominant, which shows a very marked "window" growths (also called "skeletal") in the rhombohedron faces. In the prism, underdeveloped, we can see echeloned to parallel growths. Excellent glassy luster. With inclusions those are very common in this type of quartz crystals. These specimens were collected near the Urrúnaga reservoir in Legutio. Nowadays it is near impossible find these specimens.