This was a boon to quarriers, who found little difficulty separating slabs of the stone from the vein of rock. While the calcite found in limestone produces only various shades of white or off-white, sandstone is not bound by this color. Other materials encased in the silica render sandstone a wide variety of colors, and some are quite striking. Every shade of brown imaginable is there, along with many shades of red. Some of the green hues are very attractive, and in Ulster County, New York, an unusual shade of blue sandstone was quarried.
Granite is an igneous rock, formed by volcanic action.
When molten rock, called magma, is forced from the earth's fiery core to the surface, the cooler temperature may crystallize it into granite. There are other igneous rocks, formed by other materials crystallizing in the magma, but granite is one of the best suited for building. This slow cooling process also produces intriguing geodes, semi-hollow granite rocks with beautiful crystal centers. Marble is the result of an unusual natural phenomenon. It is classified as a metamorphic rock, transformed from limestone into the soft, malleable stone used for some of the world's finest sculptures and buildings.