Desert rose (crystal)

Saharan gypsum desert rose from Tunisia (length 47 cm)
Large desert rose formation in the Tunisian desert
Baryte rose from Cleveland County, Oklahoma (size:10.2 x 7.1 x 5.5 cm)

Desert rose is the colloquial name given to rose-like formations of crystal clusters of gypsum or baryte which include abundant sand grains.[1] The 'petals' are crystals flattened on the c crystallographic axis, fanning open in radiating flattened crystal clusters.

The rosette crystal habit tends to occur when the crystals form in arid sandy conditions,[1] such as the evaporation of a shallow salt basin. The crystals form a circular array of flat plates, giving the rock a shape similar to a rose blossom. Gypsum roses usually have better defined, sharper edges than baryte roses. Celestine and other bladed evaporite minerals may also form rosette clusters.[1] They can appear either as a single rose-like bloom or as clusters of blooms, with most sizes ranging from pea sized to 4 inches (10 cm) in diameter.

The ambient sand that is incorporated into the crystal structure, or otherwise encrusts the crystals, varies with the local environment. If iron oxides are present, the rosettes take on a rusty tone.

The desert rose may also be known by the names: sand rose, rose rock, selenite rose, gypsum rose and baryte (barite) rose.

Locations

Rose rocks are found in Tunisia, Algeria, Saudi Arabia, Qatar, Egypt, United Arab Emirates, Spain (Fuerteventura, Canary Islands; Canet de Mar, Catalonia; La Almarcha, Cuenca), United States (Cochise, Arizona), Mexico (Ciudad Juárez, Chihuahua) and Australia and Namibia.

Formations in Oklahoma

Rose rock in Oklahoma was formed during the Permian Period, 250 million years ago, when western and central Oklahoma was covered by a shallow sea. As the sea retreated, baryte precipitated out of the water and crystallized around grains of quartz sand. This left behind large formation of reddish sandstone, locally called Garber Sandstone, containing deposits of rose rock.[2]

The rose rock was selected as the official rock of the US state of Oklahoma in 1968.[2]

Size

The average size of rose rocks are anywhere from 0.5 inches (1.3 cm) to 4 inches (10 cm) in diameter. The largest recorded by the Oklahoma Geological Survey was 17 inches (43 cm) across and 10 inches (25 cm) high, weighing 125 pounds (57 kg). Clusters of rose rocks up to 39 inches (99 cm) tall and weighing more than 1,000 pounds (454 kg) have been found.[3]

References

  1. 1 2 3 Desert rose on Mindat.org
  2. 1 2 "ROSE ROCK". Oklahoma Historical Society.
  3. ↑ "Noble is the Rose Rock Capital of the World". Oklahoma Tourism & Recreation Department.
Wikimedia Commons has media related to Desert rose.
This article is issued from Wikipedia - version of the 11/29/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.