The largest one ever found weighed 125 pounds. The largest cluster went over half a ton.
A rose rock is a barite rosette: an aggregate of barite and sand grown into the shape of a fully bloomed rose, with five to twenty radiating plates standing in for petals. The same habit goes by desert rose, sand rose, selenite rose and gypsum rose elsewhere, and it forms wherever crystals grow in arid sandy conditions such as an evaporating shallow salt basin. Gypsum roses tend to have sharper, better-defined edges than barite ones. Where iron oxides are in the ground, the rosettes come out rusty.
Oklahoma's came out of a vanished sea. The Oklahoma Historical Society dates them to the Permian, around 250 million years ago, when ocean water covered the western half of the state and the counties of central Oklahoma lay under shallow bays. Barite, which is barium sulphate, precipitated out of that seawater and crystallised around grains of quartz sand. As the ocean withdrew westward it left behind a band of reddish sandstone across central Oklahoma, known locally as the Garber sandstone, and the roses sit in its outcrops.
That band is where to look. Rose rocks occur from southern Lincoln County through eastern Oklahoma and Cleveland counties and on into McClain and Garvin, roughly the stretch from Guthrie to Pauls Valley, and they turn up prolifically east of Noble and Norman. Barite deposits also occur in the Wichita and Ouachita mountains, and similar rosettes are found in Kansas, California and Egypt.
Most are small, running from the size of an English pea to about four inches across, single blooms or clusters. The record-holders are something else: a single specimen seventeen inches wide, ten inches high and 125 pounds, and a cluster of more than a thousand pounds.
The state made it official. The barite rosette has been the state rock of Oklahoma since House Bill 1277 passed the legislature on 8 April 1968 and was signed by Governor Dewey F. Bartlett. Much of the ground is private, so ask before you dig.
Barite rose (state rock)
Other places on the map within a couple of hours.
