SLATE   

Fossil rock, dense, fine grain, formed by the metamorphism of shale or clay, and in some cases from igneous rocks. The principal characteristic of slate is how it splits into thin, broad sheets. The minerals that form the slates, are mainly quartz and muscovite. The slate tends to be of bluish black color or grayish black, but exist red varieties, green and other tones. Slate used in roofs, flooring and even for decorative elements.

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