276 NEW ZEALAND NATURE-STUDY BOOK 
cracks, veins, and fissures in rocks. When the Quartz-filled 
fissure is large, the deposit is known as a lode or reef. 
All those living at or near gold-mining centres will be 
familiar with this form of the mineral. The white sand 
along the sea-beaches consists almost entirely of Quartz, 
the hard mineral being able to withstand the action of 
atmosphere and sea, under which the other rock-ingredients 
disappeared, 
Uses. There are several varieties of Quartz called by 
different names: amongst the best known of these are 
Rock Crystal, or transparent Quartz, which is used in 
jewellery and for spectacle glasses; and Amethyst, a 
purple or violet-coloured transparent variety, largely used 
in jewellery. 
VII.—CALCITE (Ca.CO.,). 
One of the best known of the commoner minerals is 
Calcite, this being the name given to the purer forms of 
crystalline Limestone. It occurs in great quantities in all 
Limestone districts, both in masses shewing well-defined 
crystal form, and in pendant columns known as stalactites. 
It is also found in many places filling veins and crevices in 
rocks. 
For purposes of examination, specimens containing 
characteristic crystals, as well as those showing crystalline 
structure, should be obtained, the latter to be made use 
of in applying those tests which require the specimens to 
be broken. 
Observe the general shape of the specimen, its colour, 
which is usually white, and its lustre, varying from 
glassy to dull. Notice whether it is transparent, 
translucent, or opaque — this will depend on the 
