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Hence we see that granite consists of a mixture of three substances, called quartz, felspar, and mica, the felspar being in greatest quantity. Each of these substances possesses properties more or less peculiar to itself, such as hardness, solubility in acids, specific gravity, crystalline form, way of splitting, etc. Hence, each of these substances has a definite chemical composition and constant physical properties which define them as minerals.

This definition may be understood to include such substances as coal and chalk, which are the mineralized remains of plants and animals respectively. Even water and gases of the atmosphere may be said to belong to the mineral kingdom of nature, as plants and their parts are said to belong to the vegetable kingdom, and animals and their parts to the animal kingdom.