Rockhounding in Ohio – What Rocks You Can Find and Where

Exploring Ohio Geology

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Calcite

Streak: White

Hardness: 3

Chemical Formula: CaCO₃

Calcite is found commonly in ore deposits, as a cementing medium in sandstone, or in small quantities in igneous rocks.

These Calcite crystals come in a variety of sizes. Calcite can be microscopic or grow to several feet in length. It’s quite common to see excellent examples of calcite in “dogtooth” shaped crystals. These crystals have a pyramid shape. Calcite does not vary much in color. It is generally white or a pale amber.

Photo: Calcite, Dolomite by Robert M. Lavinsky is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Large example of pink dolomite with three quartz crystals growing from it

Celestine

Streak: White

Hardness: 3 – 3.5

Chemical Formula: SrSO₄

Celestine or Celestite is a mineral consisting of stronitum sulfate. This mineral is known for it’s light blue color, although it can be found in other color variations. Celestine can be found in geodes and is most often found in crystal form, but also in compact and fibrous forms.

Northwestern Ohio produces crystals of this mineral in colors ranging from white to a beautiful blue. Celestite can be found in Crystal Cave on South Bass Island

Learn More About Celestine

Gypsum

Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate. It is very widely mined and used in a huge variety of industries from Ancient Egypt to modern day. Gypsum is used in everything from drywall to fertilizer, in removing pollutants from water, and even in baking.

Gypsum can also crystallize and be found as translucent crystals of selenite. The fine-grained white variety of gypsum called alabaster is prized for its ornamental uses. It is soft and often used for carving.

Another form of gypsum is the desert rose, a flower-like form, typically opaque, with embedded sand grains.

Dolomite

Streak: white

Hardness: 3.5-4

Chemical Formula: MgCO₃

While the rock form of dolomite is common and closely resembled limestone, mineral dolomite can be found in certain places in Ohio. Found in Northwestern Ohio in association with many other minerals, dolomite can range in color from white to brown to pink.