146 
MANOANESE DEPOSITS OF INDIA : MINEEALOGY. [ PaRT I : 
which are to be regarded as two distinct varieties of the non-aluminous 
section of the amphiboles. There are also some amphiboles of more 
aluminous nature that contain small proportions of manganese, namely 
arfvedsonite, barkevikite, and phiUpstadite ; but since, judging from the 
published accounts, none of the Indian specimens are likely to come 
under any of these species they will not be further considered here. 
The data given below concerning these two minerals are taken from 
Dana's 'System of Mineralogy' and its appendix and the references to 
the original papers describing these minerals will be found in that work. 
Dannemorite. — Under this name are included the minerals to which the 
names of asbeferrite, silfbergite, and hillangsite have been given. All the 
occurrences of this mineral are at Swedish localities. In colour the mineral 
varies from ash-grey through greyish white, greenish grey, and brownish 
grey, to yellowish brown and dark yellow, the different colours correspond- 
ing, no doubt, to the differences in composition of the different specimens 
analysed. The mineral is in one case described as being fibroas or 
columnar like asbestos. The variety silfbergite is distinctly pleochroic, 
and has an extinction angle on b of 13° 45', and has G = 3'446 and H = 5'5. 
The four analyses quoted by Dana show the following range in the 
amounts of the various constituents : — 
Si02 46-25— 48-89 
AI2O3 0—1-46 
FeO 28-17—40-40 
MnO 8-34—12-08 
MgO 2-92— 8-39 
CaO 0-73— 3-22 
from which it will be seen that the chief constituents are silica, and 
ferrous and manganous oxides, alkalies being absent. 
Richterite. — Under this name are included the varieties known as 
marmairolite and astochite. The colour varies considerably in the different 
kinds, richterite being brown, yellow, or rose-red, marmairolite yellow, and 
astochite blue to greyish violet. The extinction angle c .\ c is given 
as 17° to 20° for richterite, whilst the extinction angle of astochite is 
given as 15° 40' for the blue crystals and 17° 15' for the greyish'-vdolet 
ones. The specific gravity of these minerals varies from 3'05-3*10. 
Six analyses quoted by Dana show the following limits of composition : — 
Si02 52-23—56-27 
AlsOs 0 —23-31 
FeO 015— 2-80 
FesOs .... 0 — 1-77 
MnO . . ... 4-86-12-71 
MgO 17-82-21-89 
CaO 5-20— 8-43 
KjO 0-66— 6-37 
NajO 2-77— 6 33 
