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Quartz. 
Quartz . — Silicon dioxide. —This mineral occurs in six-sided prisms, but most 
commonly massive. In the crystalline form it is often quite clear or coloured 
slightly yellow, when it is called false topaz, slightly purple when it is amethyst, 
slightly red called rose quartz, smoky and other tints. 
It also varies greatly in transparency from perfectly opaque to perfectly clear, 
being of various shades of yellow, red, green, blue, brown to black. Sometimes 
these colours are in stripes, bands, or clouds. The hardness is 7’0, specific gravity 
2*5, and its composition is oxygen, 53*33 ; silicon, 46*67; but the composition of 
the opaque varieties differ, as they often contain iron or earth matter. 
Quartz, although varying greatly in colour, may be distinguished by the 
absence of cleaving, its hardness, infusibility, and its crystalline form. 
Besides the vitreous varieties mentioned above, there are the Chalcedonic and 
Jaspery varieties. The first of these occurs massive, is translucent, with a waxy 
lustre, in colour usually pale greyish, bluish or brownish, often lining cavities or 
in the form of stalactites. The apple green variety is called Chrysoprase, a bright 
red or clear red tint is called Carnelian, a deep brownish, red and red by trans¬ 
mitted light is called Sard. When variegated with colour in bands, clouds, or 
patches it is called Agate, but when the colours are arranged in flat horizontal 
layers it is called Onyx. The greenish grey translucent form having an opalescence 
is called Cats’eye. 
Flint and hornstone are massive compact varieties, without any lustre. Chert 
is an impure hornstone. The Jaspery varieties differ from the others, being 
opaque, owing to a certain amount of iron or earthy matter. Jasper is dull red or 
yellow siliceous rock, containing clay and oxide of iron; sometimes the colours 
run in bands, when it is called Riband Jasper. Bloodstone or Heliotrope is deep 
green, slightly translucent, with blood-red spots. Lydian stone is a velvety 
black, opaque, and is used to test the purity of precious metals on. 
Opal. 
Opal is amorphous, stalactitic, or earthy, and owing to minute cracks in the mass, 
it often presents a play of colour of many shades. It is white, yellow, red, brown, 
green, grey, mostly translucent, but some dark varieties are opaque. It lias a 
resinous lustre, its hardness is 6*5, specific gravity about 2*0, and its composition 
consists, like quartz, of silica, but in a different molecular state, and generally 
combined with water. There are many varieties of opal, but the precious opal, which 
is milky with a pale delicate colour, is the only one of much value. Many opals 
have been found in this Colony amongst the Mesozoic rocks, but nothing of any 
value up to the present. 
Asbestos. 
Asbestos is a name given to the fibrous varieties of pyroxene and hornblende. 
It varies greatly in colour, but the white varieties are the only ones of any value, 
owing to their infusibility. It occurs in veins amongst the old crystalline rocks, 
associated with quartz, but has not been found in this Colony of a high enough 
quality, up to the present, to be worth working. The principal points are the 
length of fibre, its pliability, and its infusibility. 
Garnets. 
Garnets occur mostly crystalline of a deep red to black, green or white colour, 
transparent to opaque, with a vitreous lustre, having a hardness of from 6*5 to 7*5, 
and specific gravity of from 3 to 4, whilst their composition varies greatly. Most 
garnets fuse t-o a black glass, which is magnetic, but the chrome garnets are 
infusible. Garnets arc often mistaken for rubies, but they are easily distinguished 
by their inferior hardness, and by the fact that all red garnets fuse and blacken. 
