Pyramidal tops of quartz embedded in beige chalcedony
Pyramidal tops of quartz embedded in beige chalcedony.
Seen in episcopic white light
Seen in polarized transmitted light (crossed polarizers). Chalcedony is opaque enough to appear black, and the sectioned tops of the quartz pyramids show interference colour as they are observed in the direction of the c-axis.
Diagram of the cross section.