IMAGES OF CLAY
| Opal - spheroidal opal -A | |
| from the modern hydrothermal system at Copahue volcano, northern Patagonia, Argentina |  |
| Field of view approx. 34 microns wide | |
| Photo courtesy of Georg Grathoff, Dept. Geology, Portland State University, Portland OR, USA | |
| 640 x 528 pixel.jpg file (52 KB) - opens in a new window |
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