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.
- "Greystone" (Top Photo): Our personal favorite, greystone is the generic name given to limestone quarried in the vicinity of Bedford, Indiana. In the late 1800s, Bedford limestone became highly valued both for its durability and ease of carving/shaping, as well as its noble grey color. In Chicago, Bedford limestone was considered a premium finish used to clad middle and upper income residences particularly in proximity to the city’s park and boulevard system. Famous buildings clad in Bedford limestone include the Tribune Tower and Washington National Cathedral.
- "No So Greystone" (Bottom Photo): The other type of limestone commonly found in Chicago is Joliet-Lemont limestone. Quarried, as the name implies, in the region around Joliet in the Des Plaines Valley southeast of Chicago, this stone was used most commonly in the mid-to-late 1800s before being supplanted by Bedford limestone. Joliet-Lemont limestone fell out of popularity because it tended to be less durable than Bedford limestone and weathered from grey to a more yellow/tan color due to its high iron content. The most famous Joliet-Lemont limestone clad building in the Chicago is the Chicago Avenue Water Tower.
- "Brownstone" (Middle Left Photo): Brownstone is the generic term given to a variety of brown sandstones, primarily quarried on the East Coast and, to a lesser extent, in northern Wisconsin. Ranging from darker to lighter in tone, use of brownstone was fairly uncommon in Chicago due to its sourcing cost relative to the nearby limestone quarries of Bedford, Indiana. Thus, Chicago is considered a greystone city while New York is synonymous with brownstones. You will virtually always find a brownstone-clad home adjacent to a greystone in Chicago.
- "Redstone" (Middle Left Photo): Redstone is the generic term for a variety of red sandstones occasionally used to clad homes in Chicago. Sources for the stone included the historic Seneca Quarry in Montgomery County, Maryland. Far less common than their greystone or brownstone counterparts, redstone homes often have significant issues with the maintenance of their facades (e.g., erosion, spalling, staining) due to the poor durability of this type of sandstone.