Marble, a metamorphic rock composed principally of calcite, is found in western Vermont. The marble in Vermont was formed by the metamorphism of Cambrian to Ordovician age limestones. Marble from Vermont's Danby quarry has been used in famous buildings such as the Thomas Jefferson Memorial in Washington, D.C., the United Nations Building in New York, and the Chiang Kai-Shek Memorial in Taiwan. Most marble currently quarried in the state is crushed and used as filler in paint, paper and plastic. Slate, also a metamorphic rock, is quarried in southwestern Vermont.
Slate is a very fine-grained rock composed mainly of quartz and mica.
Vermont slates formed about 475 million years ago during the Taconic Orogeny, a period of mountain building. When sedimentary rocks, such as shales or siltstones are metamorphosed, they become slate. Slate is on the roof of the Vermont State House. Slate is used for flooring and as crushed product. Granite, an igneous rock, occurs as small to large plutons in eastern Vermont.