Where Does Coal Come From?
Coal comes from the remains of trees, shrubs, and plants that grew millions of years ago, in tropical wetlands, such as those of the late Carboniferous period (the...
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What Is Shale?
Shale is a fine-grained, earthy, sedimentary rock rather like clay, but, unlike clay, it is formed in thin layers. It is usually harder than clay and does not so easily...
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What Are Geodes and How Do They Form?
What Are Geodes and How Do They Form? Geodes are spherical rocks that contain hollow cavities lined with crystals. The name geode comes from the Greek word Geoides,...
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