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Essay / Research Paper Abstract
An 8 page overview of the geological and physical characteristics of opals. As do all gemstones, opals vary significantly in value. This is determined both by the natural characteristics of the stone and by the degree of enhancement that is employed. Bibliography lists 4 sources.
Page Count:
8 pages (~225 words per page)
File: AM2_PPgemOpl.rtf
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Unformatted sample text from the term paper:
Opals represent some of natures most brilliant work. These stones are poikilitic and can take sand into their structure or even
replace fossils, wood, shell, or bone (Pough, 1998). Consequently, opals can vary considerably in its form. The more common form is amorphous as opposed to crystalin. The
exception occurs when an opal psuedomorphs into crystals (Pough, 1998). Because of their nature, opals can range tremendously in form, color, and value.
Geologically, opal is deposited in association with hot water such as that spewing from hot springs and geysers (Lynne and Campbell, 2003; Jones and Renaut, 2003).
Geyser vents and hot springs alike are characterized by a concentration of cauliflower like masses of geyserite, a substance made up primarily of amorphous silica, i.e. opal-A (Jones and Renaut,
2003). Transgenesis to opal can occur between distinct geological layers and serves to make these layers indistinguishable (Lynne and Campbell, 2003). Lynne and Campbell (2003) observe that typically
low-temperature palisade microfacies: "display thick sheaths (>3 µm diameter) and coarse tubular filament moulds >5
µm in diameter, whereas mid-temperature bubble mat microfacies characteristically consist of thin sheaths (~1 µm diameter) with fine moulds < 3 µm in diameter".
With the transformation to opal these distinct deposits can no longer be recognized (Lynne and Campbell, 2003).
As would be expected, concentrations of opals are found in Yellowstone National Park, Virgin Valley, Nevada, Idaho, North Carolina, California, Oregon, Czechoslovakia, Japan, the
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