Name/Title
OpalEntry/Object ID
2013.2.20Description
Chemical Composition: SiO2 *nH2O
Crystal System: Orthorhombic System
Description: Common Name: Opal
Chemistry: SiO2*nH2O
Class: Mineraloid
Location: Virgin Valley, Nevada
Description: Polished face, back and sides. Brown with some pink and creme colors. Blues and red lines visible throughout. Top is apexed.
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
2-11/16 inDepth
1 inLength
8-1/2 inLocation
Category
PermanentMoved By
Curtis GardnerDate
May 25, 2023Notes
Added current locationLocation
Cabinet
Case# 70Wall
CenterBuilding
Freida Smith HallCategory
Permanent
