Chap. V. ] 
WIXCHITE. 
155 
To obtain material for the chemical examination of this mineral was 
, , a matter of considerable difficulty. The rock 
Separation of the , 
niinenil. chosen for this purpose was the wmchite-schist 
composed of winchite, calcite. quartz and 
braunite. This wa^ broken up to pass a 100-sieve and after remo\-ing the 
greater portion of the quartz and calcite by means of Soustadt's solution, 
of such a strength that most of the amphibole and braunite sank and most 
of the quartz and calcite floated, the impure mixture of bratmite and am- 
phibole was treated \vith concentrated Sonstadt"s solution (G=3'25) and 
separated into two portions, one being chiefly amphibole and the other 
a mixture of amphibole and bravmite. The amphibole in the latter 
fraction contained an abundance of included black granules tending to 
show square outlines and doubtless to a large extent braunite, though 
some of it may have been some indefinite oxide of manganese produced 
by alteration of the mineral. It was doubtless to these inclusions that 
this amphibole owed its higher speciric gra\-ity. rather than to an appre- 
ciably different composition : for although, as seen under the micros- 
cope, the majority of the cr\-stals seemed to be of the t^^pe I have describ 
ed as basic, yet there were also some of the acid ones and some of the 
composite zoned indi\iduals. The amphibole that floated in Sonstadt's 
solution contained abimdance of inrluded and attached calcite and 
much less of the included manganese-ore. The amphibole itself 
seemed to consist of the basic and acid varieties, with some of the com- 
posite zoned indi^"iduals. Tiiis porriou of the amphibole was then 
treated with Sonstadt's solurion of specific graN'ity 2 "959 in which it 
nearly all sank. The material that sank was then left overnight in 
hydrochloric acid diluted to over 1 in 50, to remove the adherent calcite. 
From an examination of the amphibole imder the microscope I do not 
bhink that this acid attacked the amphibole to any appreciable extent. 
The amphibole was then treated with a solution of specific graWtv 3 024, 
in which most of the mineral floated, whilst a portion remained suspended, 
and some sank. The portion that floated was examined imder the 
microscope and found to be very nearly free from included rnanganese- 
3re. It was subjected to one or two more separating operations and 
then used for analvsis, the amount so available being 0"383 jrrammes onlv. 
The separated material was carefully examined under the microscope 
and it was foimd that the majority of pieces, which were in the form of 
small prismatic cliips, were transparent and quite free from inclusions. 
The few inclusions present were evidently braimite : but they were so 
small in comparison with the volume of the amphibole that I do not 
