I 



Ransome.] LdWSOtlite. 3O9 



Before the blowpipe the mineral fuses readily at 2.5 to 3 of Von 

 Kobell's scale, with swelling and exfoliation to a white or light gray 

 vesicular glass, and gelatinizes readily with hydrochloric acid after 

 fusion. The unfused mineral is only slightly acted upon by boiling 

 with concentrated hydrochloric acid, but is completely decomposed 

 with the separation of gelatinous silica by heating it in a sealed tube 

 with the same acid for eight hours, at a temperature of 140 C. 

 Abundant water is given off in a matrass at a red heat, and does not 

 re ict acid. With cobalt nitrate it gives the reaction for alumina, 

 and affords a silica skeleton in a salt of phosphorus bead. 



PLACE OF LAWSONITE IN CLASSIFICATION. 



It will be seen that the new mineral falls into the second division 

 of the subsilicates as classified by Dana in the last edition of the 

 "System of Mineralogy," having an oxygen ratio of 2 : 3, and thereby 

 suggesting some highly interesting analogies with the mineral 

 carpholite. The latter has a composition of H J MnAl.,Si 2 0,„, the 

 water being constitutional, and is regarded by Groth as a basic 

 metasilicate. Lawsonite differs from it in composition by having 

 the manganese replaced by calcium. Carpholite is said to crystallize 

 in the monoclinic system, but there appears to be some doubt of 

 this fact. The similarity in chemical composition and the probable 

 identity of molecular structure is suggestive of the possibility of the 

 two minerals being isomorphous, and the suggestion is strength- 

 ened somewhat by the inconsiderable difference in the prism angles, 

 that of carpholite being 68° 33', while the acute prism angle of 

 lawsonite is 6j° 16'. 



Carpholite is optically negative, while lawsonite is positive. In 

 regard to general habit, too, and physical properties, carpholite 

 appears to be very different from lawsonite, but the comparison of 

 the two is certainly interesting and suggestive. 



ASSOCIATED MINERALS. 



The most abundant mineral immediately associated with the 

 lawsonite is the lustrous greenish-white micaceous mineral, in which 

 most of the larger crystals are embedded. The folia are small, two 

 or three millimeters in diameter, decidedly brittle, and possessing a 



