Engineering Term of the Month Granite
Granite is a common type of intrusive igneous rock that forms when magma cools slowly beneath the Earth’ s surface. It is the most widespread plutonic rock in the crust. Granite is mainly made up of quartz, plagioclase feldspar, and alkali feldspar. In places like New England, the granite often contains more alkali feldspar than plagioclase.
The color of granite can range from pink to gray. Pink shades come from potassium-rich feldspar, while gray shades result from a mix of quartz and feldspar.
Granite is very strong and durable because of its interlocking crystals, which develop during the slow cooling process. This makes it highly resistant to scratching and wear, which is why it is commonly used for building and countertop surfaces.
In engineering, granite’ s properties are measured with values like elastic modulus and Poisson’ s ratio. The Federal Highway Administration notes that granite typically has an elastic modulus between 0.93 × 10⁶ and 15.5 × 10⁶ psi, and a Poisson’ s ratio ranging from 0.09 to 0.39.
New Hampshire is famously known as the“ Granite State” because of its large deposits and extensive use of granite in construction and monuments. The abundance of granite there has shaped both the state’ s history and its nickname.
Photo: https:// pubs. usgs. gov / of / 2003 / of03-221 / htmldocs / bedrock _ photos / 82mw0001. htm
• https:// www. britannica. com / science / granite
• https:// www. zmescience. com / feature-post / natural-sciences / geology-and-paleontology / rocks-and-minerals / granite /
• FHWA Publication No. FHWA NHI-06-088, December 2006, Soils and Foundations Reference Manual – Volume 1