The slower the rock cools, the more crystals it will have. Most igneous rocks have crystals. An important rock for the Chumash and other Indians was obsidian - a glass formed from rapidly cooled lava. It formed so quickly that there is no time for crystals to grow. Although there is a lot of volcanic material at Stunt Ranch, there is no obsidian.
Granite forms as a volcanic material deep under the earth and cools very slowly.
It is composed of quartz, silica and oxygen. It is hard because of the silica which also happens to be the most abundant mineral on earth. When rocks are weathered and eroded they break down into smaller pieces of rocks and minerals. These materials, which are called sediments, may eventually be carried to a new site by wind or water and deposited, often in the sea or in river beds. The sediments are deposited in layers which become buried and compacted.