Jump to content

File:Precious opal (Coober Pedy Opal Field, South Australia).jpg

Page contents not supported in other languages.
This is a file from the Wikimedia Commons
From Wikipedia, the free encyclopedia

Original file (1,011 × 1,480 pixels, file size: 1.26 MB, MIME type: image/jpeg)

Summary

Description
English: Precious opal (Coober Pedy Opal Field, South Australia)

Opal is hydrous silica (SiO2·nH2O). Technically, opal is not a mineral because it lacks a crystalline structure. Opal is supposed to be called a mineraloid. Opal is made up of extremely tiny spheres (colloids - www.uwgb.edu/dutchs/acstalks/acscolor/OPALSPHR.jpg) that can be seen with a scanning electron microscope (SEM).

Gem-quality opal, or precious opal, has a wonderful rainbow play of colors (opalescence). This play of color is the result of light being diffracted by planes of voids between large areas of regularly packed, same-sized opal colloids. Different opalescent colors are produced by colloids of differing sizes. If individual colloids are larger than 140 x 10-6 mm in size, purple & blue & green colors are produced. Once colloids get as large as about 240 x 10-6 mm, red color is seen (Carr et al., 1979).

Not all opals have the famous play of colors, however. Common opal has a wax-like luster & is often milky whitish with no visible color play at all. Opal is moderately hard (H = 5 to 6), has a white streak, and has conchoidal fracture.

Several groups of organisms make skeletons of opaline silica, for example hexactinellid sponges, diatoms, radiolarians, silicoflagellates, and ebridians. Some organisms incorporate opal into their tissues, for example horsetails/scouring rushes and sawgrass. Sometimes, fossils are preserved in opal or precious opal.

Locality: unrecorded/undisclosed site in the Coober Pedy Opal Field, north-central South Australia State, southern Australia
Date
Source flickr
Author James St. John

Licensing

This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/34386716332 (archive). It was reviewed on 3 July 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0.

3 July 2019

w:en:Creative Commons
attribution
This file is licensed under the Creative Commons Attribution 2.0 Generic license.
You are free:
  • to share – to copy, distribute and transmit the work
  • to remix – to adapt the work
Under the following conditions:
  • attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.

Captions

Precious opal

Items portrayed in this file

depicts

6 May 2017

0.01666666666666666666 second

18.6 millimetre

image/jpeg

1,323,006 byte

1,480 pixel

1,011 pixel

87fd47bbf95d33671a1dfa7a78fc3849013fc217

File history

Click on a date/time to view the file as it appeared at that time.

Date/TimeThumbnailDimensionsUserComment
current07:46, 3 July 2019Thumbnail for version as of 07:46, 3 July 20191,011 × 1,480 (1.26 MB)EpipelagicUser created page with UploadWizard

The following 2 pages use this file:

Global file usage

The following other wikis use this file:

Metadata