QUARTZ 275 
VL—QUARTZ (Si.0,). 
In most of our mining districts, as well as in many 
others, Quartz is extremely plentiful—so that there should 
be no difficulty in obtaining suitable specimens for 
investigation. These should include some well defined 
crystals, as well as others showing the massive form of the 
mineral. 
Notice the colour and general shape of the specimen 
under review—the colour will vary with the specimen. 
The crystalline form, when pure, is colourless ; but it is 
more frequently coloured by impurities. Notice its glassy 
lustre, and determine whether it is transparent, 
translucent, or opaque. ‘These properties will depend 
on the special specimen examined. 
Ascertain that the mineral is not brittle, a considerable 
effort being required to break it; also that it is extremely 
hard—an average knife blade being readily scratched by 
it. Quartz is the hardest of all the commoner minerals, 
and can usually be identified by this property alone. In 
any scale of hardness prepared by the pupils, it wil 
probably stand at the top. 
Chip a piece off one of the specimens which do not show 
crystalline form, and observe the conchoidal fracture, and 
entire absence of cleavage. 
Notice that the mineral is crystalline, and make out the 
form of a few of the most perfect crystals — six-sided 
prisms, capped by six-sided pyramids. Determine, if 
possible, its specific gravity. Ascertain by trial that it is 
tasteless, inodorous, does not burn, is insoluble and 
infusible. 
Occurrence. Quartz, which is pure Silica (oxide of 
Silicon), occurs as an essential constituent of many rocks, 
é.g., Granite and Rhyolite. It is also found filling up 
