State Rocks, Minerals, and Gems


Idaho has no state rock or mineral.

State gem: star garnet
These dark purple silicate crystals are found in great quantity in only two places in the world: India, and Idaho’s panhandle. Star garnets have a unique property that causes them, when polished, to display a reflection that looks like a four- or six-pointed star.


Montana has no state rock or mineral.

State gems: Montana agate and sapphire
Montana agates are usually light yellow or clear in color, and contain bands and inclusions of red and black iron and other mineral oxides. They are found in Pleistocene-aged gravel deposits around the Yellowstone River and its tributaries. Montana sapphires are found in four major areas: the Missouri River, the Sapphire Mountains, Yogo Gulch, and Deer Lodge. These gemstones appear in a greater variety of colors than sapphires found anywhere else in the world, leading to Montana’s nickname as the “Treasure State.”


State rock: prairie agate
Prairie agate is a semiprecious variety of chalcedony known for its lack of the coarse banding present in most types of agate. It is found in abundance in the Ogalalla National Grasslands.

State gem: blue agate
This dark blue variety of chalcedony often exhibits blue and white banding. Blue agates formed from wind-blown silt and claystone deposited during the Oligocene and are found in northwestern Nebraska.

North Dakota

North Dakota has no state rock, mineral, or gem.

South Dakota

South Dakota has no state rock.

State mineral: rose quartz
This silicate mineral is found in great quantities throughout the Black Hills. It was first discovered there in 1875, and the Scott Rose Quartz Mine was opened in 1902.

State gem: Fairburn agate
These colorful silicate minerals are named for a locality near Fairburn, South Dakota, where they were originally discovered. The Fairburn agate is notable for its variety of colorful, strikingly contrasted, thin red, pink, white, and yellow bands.


Wyoming has no state rock or mineral.

State gem: nephrite jade
This green stone was first described in the Granite Mountains of central Wyoming in 1936. Wyoming’s jade is considered to be some of the world’s finest nephrite, and it appears in many varieties and colors.