Attention is called to a stone of different composition than any heretofore recorded, and but recently possible of identification by petrographic‐microscopic means through the work by Bowen and Morey on the system Na 2 SiO 2 ‐CaSiO 3 ‐SiO 2 . Various ways by which attempts were made to determine the composition of the crystals are described and a summary of the optical properties of these crystals from three sources is given. Probable places for the formation of these stones in the tank are also indicated.
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Albert B. Peck (1926) studied this question.