Chap. VI. ] 
CALDERITE. 
183 
were obtained is not specified. He distinctly states that calderite is a 
rock composed of two minerals. One of these is quartz, the other 
being a mineral which, to judge from his descriptions and the analysis he 
gives, must be a garnet. The hardness of the rock that he analysed 
is given as 7 to 8 and the specific gravity as 3 65, the garnet being 
evidently the principal mineral and the quartz only present in 
comparatively small amount. As the fresh fracture of the rock is 
described as being exactly like black rosin, whilst splinters are described 
as being 'sometimes highly translucent like dark brown rosin ', it is 
evident that the garnet must have been one of the very dark brown 
varieties approaching melanite in appearance. In fact, in a subse- 
quent paper 3, in which he describes a series of specimens of calderite, 
ranging from quartz containing only a small amount of the garnet up to 
rocks probably entirely composed of garnet, he particularly says, 
regarding the rock composed mostly of quartz, that the iron and 
manganese mineral in the rock is ' seen only in smaU and minute 
rounded specks like Melanite garnets '. 
In the former paper he gives the following analysis of the rock com- 
posed mostly of the garnet 
Silex 46-35 
Alumina ....... 0'35 
Lime 1-00 
Arsenic 0'20 
Perox. Iron 3018 
Protox. Manganese ..... 2100 
99- 08 
Loss, partly fluor're, of which there are traces 0-92 
100- 00 
Mallet, in discussing this analysis in his Mineralogy of India, p. 90, 
notes that the excess of silica above that which 
Composition. 
would be present m a garnet may be due to 
the quartz that Piddington says was disseminated through the speci- 
men. He also remarks on the fact that the ratio of peroxides 
to protoxides is quite wrong for a garnet, and on this account ' and 
the inaccuracy of one or two other analyses by the same author " 
regards the above analysis as very doubtful. This is an unnecessary 
1 Jotir. A'i. 8oc. Bang., XX, pp. 207 to 210, ( 185i). 
