42 v. W. G. Lang ford: 



The above minerals are characteristic of every sandstone examined. 



3, As biotite. Tliis occurs in several of the sandstones. It is 

 generally pleochroic from a pale greenish yellow to a darker tint. 

 In some sections it is nearly as plentiful as the muscovite. It has 

 ■the same relative size. The colour may be partly due to iron- 

 staining. In some cases it has been altered to chlorite. 



(/>). Accessory Minerals. — Tourmaline is the chief accessory. It 

 is to be found in every sandstone sectioned. It was not identificl 

 in the shales or mudstones. It occurs as rounded detrital grains 

 showing marked pleochroism from greenish-brown to colourless. 

 It sometimes shows good crystal boundaries. 



Zircon occurs in most of the sections. It is generally in more or 

 less rounded grains showing the remains of crystal faces. It is 

 Always clear and colourless. 



Rutile occurs in rounded detrital grains. These are mostly dark 

 reddish brown, but in one case a dark grey grain was identified. 



Black Iron ores occur throughout the rocks in irregular grains, 

 •either as magnetite or ilmenite. 



A certain amount of carbonaceous material may occur in some of 

 the rocks, but cannot be differentiated from the iron oxides. 



Anatase and sphene possibly occur, but their identification was 

 Slot definite, owing to the very small size of the grains. 



(c). Secondary Minerals. — Limonite is the cliief secondary mine- 

 ral. It replaces quartz and mica and probably also felspars. It 

 is responsible for the general colour of the sandstones. It is not 

 «o prominent in the shales. Pale-green chlorite occurs as an altera- 

 tion product of the biotite. Secondary quartz veins are present in 

 «ome of the sandstones. Secondary rutile occurs as fine needles in 

 tsericitic matter, possibly after biotite. 



Separation of Minerals with Heavy Liquid. 



A heavy liquid separation was undertaken to isolate other mine- 

 rals which might be represented in small quantity. A promising 

 sandstone No. 13 (see " Description of Sections ") from Studley Park 

 was crushed in a mortar and passed through a 120 mesh sieve and 

 then the fine muddy material was panned off with watej-. This 

 method of separating the fine material saved any small particles of 

 iheavy minerals Avhich might be present, but got rid of the fine 

 quartz and micas. 



The washed product was then divided into two portions by an 

 electromagnet. The demagnetised product was then again separated 

 into two portions, a heavier and a lighter by means of flotation in 



