ROCKS, FOSSILS, MINERALS, AND GEMSTONES OF THE UNITED STATES This collection contains examples of some of the rocks, fossils, minerals, and natural gemstones found in the United States Rocks are the building blocks of the earth and are divided into three classes based on the manner in which they are formed. Igneous rocks are formed from molten materials such as we see associated with volcanoes. Igneous rocks can be formed either above or below the earth's surface and are further divided into intrusive or extrusive rocks. Sedimentary rocks form either from material derived from the erosion or decomposition of existing rocks or precipitated from bodies of water. Sandstone is an example of the former and gypsum the latter. Metamorphic rocks form from the alteration of existing rocks by heat, pressure, or both. Fossils are the remains of past plants and animal life and offer an invaluable record of life as it has evolved through geologic time. Fossils are abundant in many parts of the United States and are found by many amateur collectors. The crinoid stem, for example, is of Mississippian Age or 345 Million years old. Minerals are substances of definite chemical composition. Many minerals are used in today's industries. Quartz, for example, a source of glass and copper is used for electrical wiring. Gemstones have been treasured by man for thousands of years. Gemstones should possess one or more of the following characteristics: color, durability, or rarity. These natural gems could be cut and polished into beautiful gemstones. The back of the kit box has an informative description of each specimen. Each specimen is about ½ inch in size and secured to the identification card to prevent loss.
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