Limestone

Limestone is a sedimentary rock composed primarily of calcite, a calcium carbonate mineral. It is formed from the accumulation of shells, coral, and other organic debris in marine environments. Limestone is a popular choice for architectural applications due to its versatility, durability and its aesthetic appeal. 

Much of the limestone used in Chicago architecture is Indiana limestone, also called Bedford limestone. This fine-grained, light-colored stone is known for its strength, ease of carving and ability to weather gracefully. It ranges in color from warm buff to gray and is often used for exterior cladding and architectural details.

While limestone is used for exterior cladding, it is also utilized in interior finishes, sculptures and monuments as well as decorative architectural details such as columns, capitals and moldings.  

EXAMPLES IN CHICAGO:  

1. The Palmer House: This historic hotel, a Chicago landmark, uses limestone for its exterior cladding and interior finishes. 
2. The Field Museum: The museum's exterior is clad in limestone, giving it a solid and imposing appearance. 
3. The Chicago Board of Trade Building: The building's exterior is adorned with limestone columns and other decorative elements.