Studies on the zeolites. Part IV. Ashcroftine (kalithomsonite of S. G. Gordon)

Abstract

In 1924 S. G. Gordon described as a variety of thomsonite a pink zeolitic mineral occurring as a fine crystalline powder in cavities of augite-syenite at Narsarsuk, Greenland. The material was described as orthorhombie, with two good cleavages a(100) and b(010) and a less perfect one c(001) ; no other faces were observed on the minute prismatic crystals. The refractive indices Gordon measured as ± 1.535, ² 1.537, ³ 1.545, with the optic orientation a = b, ² = ±, ³ = c, and optic sign positive. Analysis gave the figures under I (p. 307), and as these agree with the composition to be expected for a potassiferous thomsonite, apart from the high water content, Gordon regarded it as such, and gave it the varietal name kalithomsonite.