To date, there have been no great diamond windfalls, but diamonds have been found in Indiana, chiefly by people panning for gold. Since its recorded history, 38 diamonds have been discovered here; the largest was four carats in size and discovered in Brown County. A three-carat diamond was found in Morgan County.
Brown County is no Kimberley mine, but for decades, geologists have suspected a “ true diamond field ” likely exists in the crystalline rock formations and sediments to the north of Brown County and Morgan County. Small diamonds have been found near Little Indian Creek, Lick Creek, and Gold Creek. Many of the diamonds found in Indiana, while small, contained a yellowish hue; a few contained a pinkish hue, rare for diamonds.
While your best bet for finding diamonds in Indiana is to actually go hunting for gold in these particular areas, it’s still quite rare to find one. Gem hunters have a much better chance for locating other types of precious or semi-precious stones and minerals such as calcite, marcasite, and quartz. The best places to search for these are near quarries or in abandoned mines; however, the mines may be located on private property and could be unsafe to enter in any case.
Aside from geodes that are popularly found in Brown, Monroe, and Lawrence Counties, pyrite is found in abundance in the southwestern part of the state. Dubbed “fool’s gold,” pyrite is a mineral that only has a superficial similarity with gold. Its yellowish-brassy hue has a metallic luster easily confused with gold. Though more brittle than gold, pyrite is used to create jewelry, but it has also been used historically to ignite firearms and as a component in radio receivers.
The presence of gems and minerals in Indiana has much to do with the region’s glacial history. One theory is that the diamonds were washed southward in material that existed in the Canadian wilderness, north of the Great Lakes. Geologists suspect the diamond-containing matrix to have been large for so many diamonds to be found scattered in Indiana.
Above Indiana map courtesy of Earlham College (great additional info HERE)
The shifting of land and water from Lake Chicago likely transported swathes of this material, much of which seems to have washed up in Brown County. Many of the other minerals found in the state are often discovered near limestone formations after quarries have been dug.