2. Granites are generally massive in form, and compose the main part of most mountains. They are hard and granular in structure, the principal constituents being feldspar, mica, and quartz, in varying proportions. A granite containing much quartz is very refractory to work; as the proportion of quartz becomes less and that of feldspar increases, the stone works correspondingly easier.

The color of granite depends chiefly on that of the feldspar, but frequently it varies with the quantity of light or dark mica contained in it. It is usually grayish in color, but may be obtained in all shades, even light pink and red being found in different localities. The light, fine-grained varieties are the most durable, but nearly all kinds have ample strength for ordinary purposes.

2.

Granite may readily be quarried, as it breaks with regularity, and can usually be obtained of any required size. Great difficulty, however, is experienced in working granite, owing to its hardness and toughness, which make it very expensive to cut, and prevent its use in fine carving. Granite is probably the best stone for foundations, etc., and is extensively used in other positions requiring great strength, besides being put to such minor uses as flagging, thresholds, water-tables, etc.

All kinds of granite are damaged considerably by the action of fire, which causes them to crack badly. They disintegrate at temperatures ranging from 900° to 1,000° F.

Very good varieties of granites are found in many places in this country. Those of the Eastern states are probably the best known, but many other sections of the United States have stone in every way equal to them. Valuable quarries of granite are found at Vinalhaven and Hallowell, Me.; Quincy, Mass.; Concord and North Conway, N. H.; Westerly, R. I.; Barre, Vt.; St. Cloud, Minn.; Granite-ville, Mo.; in Colorado, Georgia, and numerous other places.

3. Gneiss (pronounced nice) is constituted similarly to granite, but is distinguished from it by the somewhat parallel arrangement in layers. Owing to this peculiarity, the rock splits into slabs having approximately parallel surfaces, making it valuable for walls, street paving, etc. Gneiss is called by quarrymen stratified, or bastard, granite.

4. Syenite differs from granite and gneiss in containing no quartz. It is hard and durable, usually having a close texture, and a light-gray color. Like them, it is a very good building stone, and, except as above mentioned, has the same characteristics.