A Geoscience Digital Image Library
A Geoscience Digital Image Library
| Title | Opal |
|---|---|
| Description | Opal is a mineraloid because its structure is not truly crystalline. Opal's chemistry is SiO2-nH2O. The amount of water in opal varies from 5-10% and greater. This water can help geologists determine the temperature of the host rock at the time the opal formed. Opal's environment is sedimentary and secondary from the alteration of high silica igneous extrusive rocks. The most striking quality of opal is its ability to refract and reflect specific wavelengths of light or its “opalescence”. The size and spacing of the amorphous spheres of silica within the stone refracts specific wavelengths of light; each sphere refracting a single, pure spectral color much like the individual microscopic droplets of water in a rainbow. |
| Location | Mexico. Near Gueretaro. |
| Photographer | Shannon Heinle. 2001-07-25. |
| Collection | University of North Dakota Mineralogy Collection #1638. |
| Key words | opal, mineraloid |
| Tech details | 463 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. |
| GeoDIL number | 1379 |
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