Opal

Object/Artifact

-

Crater Rock Museum

Opal

Opal

Name/Title

Opal

Entry/Object ID

2013.2.14

Description

Chemical Composition: SiO2 *nH2O Crystal System: Orthorhombic System Description: Common Name: Opal Chemistry: SiO2*nH2O Class: Mineraloid Location: Australia Description: Opalized "shell" with a light gray matrix and a polished face. Light tan to light brown lines throughout. Opalized lines on face of specimen which resembles a shell. (Could be a shell) 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: White

Collection

RAGM Mineral Collection

Acquisition

Accession

LN 2013.2

Dimensions

Width

4 in

Depth

1/4 in

Length

3-1/4 in

Location

Location

Cabinet

Case# 70

Wall

Center

Building

Freida Smith Hall

Category

Permanent