State Rock

Yule Marble is Colorado’s State Rock

At the urging of a Girl Scout Troop, Representative Betty Boyd introduced a bill to make Yule Marble Colorado’s official State Rock. As legislators considered the proposal, they were never very far from the real thing, because some of the floors and trim in the State Capitol Building are made of Yule Marble. It has also been used in the construction of more than 30 buildings in Colorado and more than 100 buildings across the country including the Lincoln Memorial and the Tomb of the Unknowns.

Cogent points about Yule Marble:

  • The stairs and floors of the State Capitol Building were supposed to be made of Yule Marble.
  • The stone was used in the construction of more than 30 buildings in Colorado and more than 100 additional buildings across the country including the Lincoln Memorial and the Tomb of the Unknowns.
  • It is possible to quarry larger blocks of Yule Marble than most other marbles in the world.
  • The character of the stone is exceptional and is better for sculpting than Michelangelo’s favorite Carrara Marble.
  • Its chemical purity, as well as its small and uniform grain size has led to its use in many experiments in rock mechanics.

The story of how Yule marble became Colorado’s State Mineral

Inside the underground Yule quarry

Inside the underground Yule quarry.

Governor Bill Owens signs the bill that makes Yule Marble Colorado’s official state rock.

Governor Bill Owens signs the bill that makes Yule Marble Colorado’s official state rock on March 9, 2004.

Presentation about Yule Marble (video)

Fact Sheet on Yule Marble from Girl Scout Troop 357:


Colorado is the Centennial State. Colorado has a red Official State Mineral, rhodochrosite. Colorado has a blue Official State Gemstone, aquamarine. If the state rock were white, the Official Geological symbols would be red, white, and blue. The Yule Marble is white. The Yule Marble has been used in many famous buildings and sculptures.

  • The Lincoln Memorial in Washington DC.
  • In the Washington Monument, each state contributed a 20″ x 40″ rock to line the inside of the monument, and Colorado chose the Yule Marble.
  • The Tomb of the Unknowns, currently being renovated, is made of the largest single block of marble produced in the United States.
  • Colorado State Capitol building.
  • Cheesman Memorial, Denver.
  • Colorado State Museum, Denver.
  • Denver Court House.

As the state known for the majestic Rocky Mountains, it seems odd that the state does not yet have an official state rock. Only nine states have three geological symbols (rock, gem and mineral), and none of them have the color combination of red, white, and blue. Only four states have a state rock that matches the rock in the Washington Monument for that state. The Yule Marble is a strong, beautiful rock. It is composed of 99.5% pure calcite. The grain size yields brilliant cleavage sparkles in the unpolished stone. It has lasted almost 100 years in the humid environment of DC. The first major use of the Yule Marble was in the Colorado State Capitol building, in 1895.