BY H. C. RICHARDS. 109 



A microscopical examination of this rock shows it to 

 have an even-grained granitic structure and to he of medium 

 grain-size. The quartz and felspar cr3'sta]s are about 

 2 mm. long while the average biotite flake is 1mm. long, 

 but flakes occur up to 2.5 mm. in length. 



The minerals present are qiiartz, plagioclase, ortho- 

 clase, biotite, chlorite and magnetite in decreasing order 

 of abundance. The quartz and plagioclase are approxi- 

 mately equal in amount (see microphotograph lo. plate X). 

 The biotite has to some extent been altered into chlorite, 

 but generalh^ speaking it is fresh. The plagioclase is 

 occasionally cloud}- but as a rule it is clear. It shows 

 zoning to a ver^- great extent and is acid andesine. The 

 magnetite is present in very occasional inclusions in the 

 biotite. A noticeable feature is the compa^ati^'e scarcitj'' 

 of biotite. Pyrites is absent. 



This granite has been used in the Technical College 

 erected at Warwick a few ^ears ago, in the base and as a 

 kerbing along the front drive. The base of the Government 

 Savings Bank, Brisbane, is composed of this material and 

 lately it has been used as kerb stones alongside the tram- 

 rails in parts of George and Queen Streets, Brisbane. 



Magnetic Island " Graniie." 

 This is a \ery light-coloured granite with a pale pinkish 

 tinge which is derived from the felspars. It is of medium 

 grain and is composed of quartz, felspar, biotite, horn- 

 l)lende and magnetite in decreasing order of abundance. 

 The dark minerals are not plentiful enough to give the 

 rock the necessary " relief."" Biotite occurs as very small 

 flakes while the hornblende which is not abundant occurs 

 as occasional rods. The stone is clean-looking but rather 

 pale. It has been used in the ]>ase course and steps of the 

 Custom House at Townsville. 



Mackay " Granite." 

 L. C. Ball has described this as a pink to grey syenite 

 And granite of ver^- variable comjDosition and appearance, 

 occurring over an area of about 1 mile in diameter. He 

 also states that the rock has been quarried for material 

 for the breakwater at the mouth of the Pioneer River. 



