Gravel Limestone Slag Sand
Indiana Mineral Aggregates Association

What are aggregates?

Aggregates are simply any collection of rocks. In the aggregates industry, these rocks are classified as crushed stone, sand, gravel and slag.

We use aggregates every day.

Streets, bridges, roads and sidewalks are made of concrete or asphalt which is mostly made up of aggregates combined with a binder that acts like glue. Concrete is used in foundations and basements for houses. Other buildings sometimes use concrete throughout their structures.

But did you know that many items you use every day have aggregates in them? Your toothpaste has aggregates in it. Glass is made from sand, which is an aggregate. Minerals and aggregates are in plates, dishes, pots and pans, baby powder, household cleaners, makeup, medicines, paints, pencils, fertilizers, wallboard, and more including some of the foods you eat! How many times have you heard that your cereal, for instance, is fortified with vitamins and minerals?

Any object that hasnt been grown had to be mined! Aggregates, minerals and metals all come from the ground. You can look at objects all around you and know which were grown and which were mined. If its metal, it was mined. If it is wood, it was grown. If it is cotton or wool, it was grown. Paper comes from trees, which are grown. Pencils are grown and mined because wood is grown and graphite is mined. The ink on this paper came from mining. But what about plastic? Is it grown or mined? Plastic comes from petroleum products, which are mined.


A widespread but highly variable resource in Indiana that was formed mostly by glacial actions of large ice sheets and then sorted by running water. Sand can be used as fill, or more often the coarser parts find use as components of concrete or asphalt pavement. Sand, a finer granular material, also is important in concrete and in making mortar and in snow and ice control. Very fine grained sand finds use in foundries to make molds, and also in sandblasting, glass-making, or even as golf-course sand.

Looking for companies that produce SAND in Indiana? Find them in our Member Directory.


The term gravel applies to a range of particle sizes, rather than a specific rock or mineral type. Gravel is colored by the rock types present. It is a collection of rock particles that are at least .08 inches in diameter sizes, but may also include boulders over 10 inches in diameter. Gravel is loose rock that is often rounded in shape from being worn by water at some point. Gravel can be used alone as fill, for gravel roads, or residential driveways. Gravel can also be used as a component of concrete or asphalt pavement.

Looking for companies that produce GRAVEL in Indiana? Find them in our Member Directory.

Limestone (crushed stone)

Limestone is the primary rock type making up aggregate and is mined throughout Indiana. It is usually gray rock (but color can vary) consisting of at least 50% calcite. The texture can be coarse- to very-fine grained. Whole fossils or fossil fragments are typically present in limestone. Indiana is probably best known for her dimension building stone. Indiana Limestone (properly named Salem Limestone) is mined in south-central Indiana but is used all over the United States. Indiana Limestone has helped construct such iconic buildings as the Empire State Building, the Pentagon, The Washington National Cathedral, and many venerable official, commercial, or religious structures.

The more widespread and less uniform limestone in Indiana provide for excellent crushed aggregate, cement, chemical raw material, and for limited architectural uses. Aglime is produced by heating crushed stone and is used in agriculture. Check out the Indiana Aglime Council for more information on aglime.

Looking for companies that produce CRUSHED STONE in Indiana? Find them in our Member Directory.


Slag is a man-made or synthetic aggregate recycled from the steel-making process. It is a dark-colored and usually rough-textured rock. Slag makes an excellent aggregate for certain types of road construction. For example, slag is used as the surface material at the Indianapolis Motor Speedway because its angular, sharp texture creates excellent traction and skid resistance.

Looking for companies that produce SLAG in Indiana? Find them in our Member Directory.

Want to learn more about Indianas mineral resources? Check out the Indiana Geological Survey.


IMAA represents over 90% of aggregate production in Indiana. Find out what we’re doing for our members and how you can benefit from IMAA.
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IMAA members produce crushed stone, sand, gravel or slag, sell mining equipment, haul material, and much, much more.
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The Source Report – the bi-monthly membership newsletter of the Indiana Mineral Aggregates Association.

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