Application: exterior - Interior wall and floor applications, monuments, countertops, mosaic, fountains, pool and and other design projects   Granite, being an igneous rock (formed from volcanic activity), differs from marble, limestone, and travertine in that those are sedimentary stones composed mostly of calcite, a relatively soft and common mineral derived from animal skeletons and shells. Millions of years of compression and heat below the earth's surface turned them into stone. Granite is one of the hardest stones available, having a rating of 7 on the Moh's Measurement of Hardness Scale. In contrast, marble is rated only a 3. And since their main component is calcium, marble and the others are more susceptible to damage by acids such as vinegar and citrus beverages. Crushed stone is the most basic use of granite. Crushed granite is used as a subbase and base material in road and highway construction. It is used as crushed stonemedia in sewage system drain fields and as a base material for foundations and construction slabs. Crushed granite in attractive colors is used as a landscape stone and in planters. It also makes great railroad ballast, and in larger sizes it makes good riprap.