Occurs as stalactites and stalagmites in a lava tunnel.
Quality of samples:
not specified / average specimens
Anderson, Charles A. (1930), Opal stalactites and stalagmites from a lava tube in northern California: American Journal of Science, 5th. Series: 20: 22-26; Anderson, Charles A. (1931b), Opal stalactites from a lava tube in northern California (abstract): Geological Society of America Bulletin: 42: 310; Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 282; Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 356.