A Geoscience Digital Image Library
A Geoscience Digital Image Library
| Title | Fire opal |
|---|---|
| Description | Opal (rainbow colored) is considered a mineraloid because its structure is not truly crystalline. The most striking quality of opal is its ability to refract and reflect specific wavelengths of light (its “opalescence”) which gives it a play of colors. Opal's chemistry is SiO2-nH2O. The amount of water is generally 5-10% or more. The amount of water depends on the temperature of the host rock at the time the opal formed. Opal forms in sedimentary environments, and as a secondary mineral in high-silica extrusive rocks. It's name comes from the Old Indian upala meaning “precious stone.” This sample is 6 cm across. |
| Location | USA ▹ Idaho |
| Photographer | Shannon Heinle. 2001-06-18. |
| Collection | University of North Dakota Mineralogy Collection #1626. |
| Key words | opal, mineraloid |
| Tech details | 425 KB. Hand specimen. Fujifilm FinePix S1Pro digital camera; 60mm AF Nikon micro lens. |
| GeoDIL number | 780 |
 | |