The Castle Marne is one of the few houses still standing in Denver built with Rhyolite, known for it’s light color and fine-grained texture. Rhyolite is much like granite, but it is formed closer to the surface of the earth. Rhyolite is the most silica-rich of volcanic rocks, and was probably purchased from one of five quarries operating in Colorado between Castle Rock and the Palmer Divide. The rhyolite quarries employed hundreds of people a century ago – but These quarries shipped stone from the Denver and Rio Grande Railroad throughout Colorado, Kansas and Wyoming.
Rhyolite is rarely used and seen today, as cheaper building materials, such as concrete, became more available. After the silver crash of 1893, the quarries closed, leaving few structures that could still afford this beautiful stone.
Other Rhyolite building in Denver are the Dunning-Benedict Mansion and the Trinity Methodist Church, located at Broadway and 18th street.