10 THE MINERALS OF TASMANIA. 



19. Apatite ( Fhosphate of Calcium). 



This mineral crystallises in the hexagonal system, with 

 pyramidal hemihedrism. It often occurs in the massive 

 form, and it is mainly in this condition that it is mined 

 commercially on the large scale. Apatite as a microscopic 

 mineral is a widespread accessory of igneous rocks of almost 

 all kinds; the micro crystals are mainly long hexagonal 

 prisms, and it was evidently one of the first minerals in the 

 rock-forming magma to crystallise. It occurs macroscopic- 

 ally of a clear greenish colour, with a dull lustre, and, in 

 the amorphous slate, in limited quantity (mixed with the 

 veinstone) at the old Hampshire Silver Mine ; at Mt. 

 Bischoff, as small pale crystals in the stanniferous topaz, 

 porphyry ; in small crystals and crystalline particles in 

 wolframite in the Bischoff Extended Mine ; and as minute 

 crystals, about 10 millimetres in length, of a pale pinkish 

 colour, abundantly scattered throughout a stanniferous- 

 granite, at the Crystal Hill, Blue Tier. 



•20. Anthophyllite ( Me.fasilicate of Iron and Magnesium). 



This is a rock-forming mineral of extremely restricted 

 distribution, being mainly met with in Scandinavia. It is 

 an orthorhombic amphibole which apparently bears the 

 same relation to hornblende that enstatite does to augite. 

 It is peculiar to the schists, and occurs as fibrous or bladed 

 masses which are thin and without terminations. In 

 habit they are commonly aggregated together in such a 

 manner as to bear a strong resemblance to actinolite. It 

 is usually of a pale-brown colour, varying to a darker 

 shade, but may be still more rarely of a bright-green 

 colouration. It has often a characteristic semi-metallic, 

 glimmering lustre. In thin section under the microscope it 

 shows unmistakably straight extinction and distinct- 

 pleochroism. It occurs as a schist upon a mineral section 

 which was known as the Great Hercules, situated on 

 the west flank of Mt. Read. The mineral in question is of 

 a bluish-grey colour, with metalbidal lustre, and in habit 

 is often aggregated together in bunches of irregular fibres 

 and blades. The latter may be up to 1 inch in length, 

 and sometimes show an irregular radiating structure.. 

 Anthophyllite schist also occurs at a locality known as the 

 Black Bluff, at Cox's Bight, near S.W. Cape (L. K. Ward). 

 The mineral is of a grey colour, with a somewhat metallic 

 lustre, and occurs plentifully distributed throughout the- 

 rock in fine parallel blades. 



