Name/Title
OpalEntry/Object ID
2013.2.23Description
Chemical Composition: SiO2 *nH2O
Crystal System: Orthorhombic System
Description: Common Name: Opal
Chemistry: SiO2*nH2O
Class: Mineraloid
Location: Virgin Valley, Nevada
Description: A very large cut and polished specimen. Reddish-brown, tan and blues and some white.
Physical Characteristics:
•Color is white, colorless, pale yellow, pale red, gray or black when impurities are common. Diffraction can cause flashes of any color of the rainbow (play of light).
•Luster is vitreous to pearly.
•Transparency: Specimens are transparent to translucent (opalescent).
•Crystal System: Does not apply because opal is amorphous.
•Habits include massive, cavity-fillings such as in fractures and geodes, nodular, reniform or as a replacement of other minerals and wood.
•Cleavage is absent.
•Fracture is conchoidal.
•Hardness is 5.5 - 6
•Specific Gravity is approximately 2 - 2.5 (light)
•Streak is white.
•Other Characteristics: Most specimens will fluoresce white or pale green, some phosphoresce and all specimens can be very sensitive to impacts and low temperatures.
•Associated rocks are chert (a form of microcrystalline quartz), volcanic rocks and many others.
•Notable Occurrences include many Western USA localities; Mexico; Australia; England; Czech Republic and many other localities around the world.
•Best Field Indicators are color play & opalescence, low density, fluorescence, fracture filling tendency and lack of cleavage or crystal faces.
Fracture: Concoidal
Hardness: 5 Apatite
Luster: Vitreous
Rock Type: Sedimentary
Specific Gravity: 2-2.5
Streak: WhiteCollection
RAGM Mineral CollectionDimensions
Width
7-1/8 inDepth
4 inLength
16 inDimension Notes
All four eggs are between 2.00" to 2.500"Location
Category
ExhibitMoved By
Jillian Mather KettleyDate
June 11, 2024Location
Shelf
CS-F-6Room
Curation StorageBuilding
Crater Rock MuseumCategory
StorageMoved By
CuratorDate
February 16, 2024Notes
Added current location
