We tend to get a bit geeky over the architecture and construction of greystones and similar stone buildings here at the Historic Chicago Greystone Initiative, so over the next several posts we will be sharing information about the stones themselves, their various forms, architectural details, and repair best practices.

Know Your Stone: The Basic Building Blocks

Two primary categories of stone were used commonly to clad the front facades of homes in Chicago in the 18- and early 1900s: sandstone and limestone. Less commonly, due to their cost, granite and marble were used as elaborate alternatives to sandstone or limestone.

Sandstone is a sedimentary rock made of up of other weathered rocks and minerals cemented together over time. Sandstones are most commonly tan, yellow, brown, or red in color.

Alternatively, limestone is a sedimentary rock composed primarily of calcium carbonate from the remains ancient sea creatures that have been compressed and cemented. Limestones tend to be whitish or grey (at least initially) in color.

OK…Many of you are probably thinking: “Thanks for the geology lesson, but how do I know what stone was used on my house?” So here is a quick visual and descriptive primer on the most common types of limestone and sandstone you will see in Chicago. Note: The actual look and condition of your stone may vary due to painting, atmospheric pollution, and improper cleaning, but that is a discussion for a later post.