Granite is an igneous rock that is composed of four minerals. These minerals are quartz, feldspar, mica, and usually hornblende. Granite forms as magma cools far under the earth's surface. Because it hardens deep underground it cools very slowly. This allows crystals of the four minerals to grow large enough to be easily seen by the naked eye. Granite is an excellent material for building bridges and buildings because it can withstand thousands of pounds of pressure. As an igneous rock, granite is an extermely hard material. A highly polishable stone with a very large array of colors to choose from.

Marble

Marble on the other hand is metamorphic rock and is not as hard. Once limestone, marble is a product of intense pressures and high temperatures from within the earth. Will polish well, but unlike granite, marble can scratch and stain easily.

Soapstone

Soapstone is a sedimentary rock and is very soft. It is often used as carving material. It was traditionally used in Colonial New England for hearths and countertops.

Onyx

Onyx is a sedimentary rock. It is a translucent material characterized by veins running through it often in concentric patterns. Like marble it will take a high shine and is similar in hardness.