From diamonds to coal, limestone to amethyst, Indiana’s naturally occurring gems and stones vary widely. The extraction of resources like coal and limestone form the basis for the mining and quarrying industries in the state, while hobbyists collect the rarer gemstones, geodes, and gold that can be found in the state’s rivers and streams.
In 1971, the State of Indiana officially designated limestone as its state stone. The Pentagon and the Empire State Building are just a few of the famous American buildings that boast limestone that was quarried and carved in Bedford, Indiana, which is known as the “Limestone Capital of the World." Local entities usually oversee limestone quarrying, unlike the state-wide organizations that regulate mining for minerals like coal and shale.
Mining in Indiana
The type of stone that has been mined most extensively in Indiana is coal, which is burned in power plants to generate much of the state’s electricity. Indiana’s Division of Reclamation oversees the mining of coal, as well as clay, shale and oil shale, and spearheads the reclamation of land that has been used for mining. Sand, gravel and crushed stone are also commonly mined in Indiana, along with peat, marl, and gypsum, according to the Division of Reclamation.
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Gold and Diamonds
Although gold and diamonds can both be found in Indiana, they occur rarely, so there is not a significant industry around their extraction. Glaciers carried gold and diamonds from Canada into Indiana, grinding them away from their sources, and depositing them at the ends of the glacier. While neither the gold nor diamonds found in Indiana were formed there, they can still be found in the rivers and streams that drain glacial deposits.
Geodes and Gemstones
Geodes form when a layer of silica surrounds a deposit of soft gypsum salt. The gypsum eventually dissolves, leaving a spherical stone with a hollow center, and in time, minerals like quartz or calcite fill the empty space left by the gypsum. Other minerals that can occur in geodes include millerite, celestite, strontianite, barite, and amethyst. The Indiana Geological Survey recommends hunting for geodes in Indiana’s creek beds, where they most commonly occur.