Illinois is world famous for its Mazon Creek fossil deposits as well as for its fluorite deposits. Apart from fluorite, some other minerals found in Illinois are calcite and barite. There are also locations where geodes are found. Although the minerals found in Illinois are not particularly high-value compared to some types of gemstones, there are still many beautiful types that are popular for rockhounds and collectors alike.

Fluorite

Fluorite is a mineral made from calcium fluoride and is considered as the official state mineral of Illinois. Fluorite can either occur as a transparent clear crystal or can occur in different colors such as dark purple, sea green, light blue and yellow owing to other elements present in the crystal in trace quantities. Crystals are generally clear or light shades, but some brilliant crystals have also been found in Illinois.

The southeastern region of Illinois has been known to have enormous fluorite rich deposits especially occurring in veins of limestone rock formations. Pope and Hardin Counties located in Illinois were mined for fluorite deposits commercially for many years, making the state the largest producers of the mineral in the United States.

The small town of Cave-In-Rock on the Ohio River near Kentucky and Rosiclare in Hardin County have the most popular fluorite deposits. The crystals come in a variety of different colors but the most valuable are the deep purple fluorite crystals. Occasionally they are found in combination with other beautiful minerals such as sphalerite and galena.

Calcite

Calcite is a commonly occurring mineral composed of calcium carbonate. The mineral is generally found as white or colorless crystals, however it also occurs as pale yellow or grey as a result of some impurities.

The vast geode producing veins present in the towns of Hamilton, Nauvoo and Warsaw in Hancock County, Illinois are a source of calcite crystals. Calcite can be found in the cavities of limestone, dolomite and coal deposits in the southern and northwestern part of the state.

The Cave-In-Rock area and the Denton Mine located in Harris Creek District in Hardin County are other locations where calcite crystals can be found along with fluorite, barite, and a variety of other beautiful crystals.

Barite

The mineral barite is composed of barium sulfate and is the chief ore of barium. Barite generally occurs as colorless or white crystals and sometime in other colors such as red, yellow, pink, orange, brown, blue, green, purple, grey and black.

In the state of Illinois, barite is often found along with fluorite and calcite. As with many other beautiful minerals, barite is most abundant in Hardin County and some of the surrounding areas near the Ohio River in the southern portion of the state.

Fossils

Illinois has vast fossil deposits in the state’s northeastern region. The Tully Monster was designated as the official state fossil of Illinois in the year 1989. Tully monster was a marine animal which was an invertebrate that lived in ocean water. Despite its menacing name, Tully monster was not more than six inches in length with an elongated body that narrowed towards the ends. These animals belonged to the Pennsylvanian era which was about 340 million years back.

The Mazon Creek fossil area located in Grundy County of Illinois has abundant fossils of Tully monster. One can collect these fossils from the site by paying a small amount of fee, however collection of commercial purposes is not allowed. Tully monster fossils can also found in the central region of Illinois within the open pit coal mines present in the area.

Geodes

Geodes and spherical rock structures found in volcanic or sedimentary rock formations and consist of minerals in crystal form inside. The size of the geodes from Illinois varies from less than one inch and can be bigger than two feet across.

The most productive area in Illinois where geodes are found is in the western region of the state within the Warsaw rock formation. These geodes can vary in color and occasionally are hollow with crystalline formations inside of them.