Miiierals in Daciff. 531 



MicO: — By means of a bar-iaaguet al! the steel splinters ofif 

 the mortar, and grains of opaque material that would come out 

 were removed ; then the powder was subjected to the electro- 

 magnet with the pole-pieces 4 mm. apart, and all the material 

 which would come out while 3 amperes were run through the 

 magnet was removed. 



This magnetic material was made up of free grains of biotite, 

 hyperstiiene, and composite giain.s of either or both these minerals 

 with felspar and quartz, or with the magnetic opaque material. 

 By gentle shaking of the cardboard boxes held at a slight angle 

 and with one end cut away, the biotite was separated from the 

 other material, small lots being treated at a time and given 

 several shakings. 



By means of Sonstadt's heavy liquid of Spec. Gr. about 3, 

 used with a Sollas Separator, the free biotite was separated 

 from most of the other material, only a few composite grains of 

 hypersthene and iuica coming down also. The material Avas 

 then washed and dried, and the composite grains picked out 

 with a fine wet brush underneath the low power of the micro- 

 scope. This was a very laborious process, but only in this way 

 could quite pure material suitable for analysis be obtained. 



Hypersthene. — The powder whose grains were about .1 mm. 

 in diameter was used for obtaining this mineral. ^Yith a volt- 

 age of 10 (3 amperes) and pole-pieces 4- mm. apart, the mag- 

 netic material, which separated readily, was removed by the 

 electro-magnet. On bi*eaking the circuit a certain amount of 

 material still adhered to the pole-pieces, and was made up of 

 small steel splinters from the mortar, fragments of ilmenite 

 and leucoxene, and in some cases pieces of quartz or felspar 

 containing inclusions of the opaque mineral. The magnetic 

 material separated as above contained grains of hypersthene, 

 biotite, ilmenite, quartz and felspar containing magnetic inclu- 

 sions, and a fair amount of com])osite grains of the above 

 minerals. 



Under the microscope it was noticed that hypersthene grains 

 vcrv often enclosed large patches of the opaque material. 



lij- means of card-shaking the biotite was removed almost 

 completely. The remaining material was then subjected to a 

 voltage of 3 with pole-pieces 4 mm. apart, the material removed 



10a 



