This is a superb, museum size specimen of druzy chrysocolla (also called gem silica). It is a large pocket which is lined with chrysocolla, all covered with microscopic quartz crystals called druzy quartz), which give it an amazing sparkle as the tiny crystals twinkle and flash in the light.  The chrysocolla is colored a very rich, full-bodied, turquoise blue, which contrasts very nicely with the dark background.  There is no distracting damage.