74 THE MINERALS OF TASMANIA. 



of considerable intrinsic value for the manufacture of 

 microscopic objectives, which when used in conjunction 

 with Jena glass are known as apochromatic. Where plenti- 

 ful it is used as a fluxing agent in metallurgical work, and 

 is employed in the manufacture of a milky glass, as well as 

 in the production of hydrofluoric acid and various fluorine 

 compounds. The phosphorescence of fluor is a well-known 

 phenomenon, and this property is strongly exemplified in 

 that obtained at Hampshire, and also in that from Mt. 

 Bischoff. The minerals from these localities belong to the 

 variety which has been named chlorophane. Both afford a 

 clear bright pale-green when their powder is strongly 

 heated. Under the influences of radium fragments of 

 mineral from both localities instantly glow intensely with 

 a pale-green light. Well-developed crystals are not infre^ 

 quent at the Mt. Bischoff Tin Mine. They are up to 1 

 inch in size, of light amethystine colour, and are accom- 

 panied by siderite, quartz, pycnite, and (more rarely) 

 apatite. The crystals are generally octahedra, modified 

 by small faces of the cube. It is also obtained in similar 

 crystals, but mostly of light-greenish colour, in the 

 amphibolite of Mt. Ramsay, associated with scheelite and 

 native bismuth. At the Mt. Black Mine, near Rosebery, 

 the fluor is abundant in a narrow lode with chalcopyrite, 

 pyrite, wolframite, and tourmaline. It illustrates many 

 varieties of colour, from almost white to shades of purple 

 and green, the purple predominating. Some remarkably 

 fine specimens of this mineral have been obtained at the 

 Great Republic and other mines situated at Ben Lomond. 

 The crystals are individually small, but beautifully defined, 

 well and clearly cut cubes. They are from almost colourless 

 to pale-purple, with the apices of the acute angles distinctly 

 stained an intensely dark purple. Modifications of form 

 and intergrowths are not uncommon. This is at once the 

 most attractive and interesting occurrence in this island. 

 At the Thomas' Blocks Silver-lead Mine on the south bank 

 of the Murchison River much fluorite occurs in the lode, 

 intermixed with the prevailing quartz gangue ; siderite is 

 also present, but in a subordinate degree, which is unusual 

 in the silver-lead mines as occurring in this State. The 

 country-rock is slate, more or less indurated by inter- 

 polated schists ; but the lode minerals indicate that acidic 

 intrusive rocks are not far distant. The fluorite is usually 

 in fairly large masses and crystalline. Good crystallisa- 

 tions have been observed ; in colour the common tints are 

 a pale shade of bluish-green to almost colourless. It is not 



