Water at or near the earth’s surface plays an important role in the formation of some gem minerals. Surface water is capable of dissolving many minerals, particularly when provided a great deal of time to do so. As a result, it carries away components in solution that remain dissolved until, under appropriate conditions, new minerals are deposited. Precious opal and other gemstones form from surface water under special conditions that may include chemical reactions, cooling of waters previously heated by nearby molten rock, and evaporation. Rainwater, for example, combines with atmospheric carbon dioxide to produce carbonic acid, a weak natural acid. If such water seeps into the earth and encounters sulfides (such as pyrite, FeS2), sulfuric acid, a much stronger acid, is produced, which dissolves minerals, transports their chemical elements, and permeates other rocks to form new minerals.
- South Wale
- Solid Silica
- Great Artesian Basin
- Water Seep
- Opal Deposit
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Keller, P.C. (1990). Gemstones Formed from Surface Water: The Opals of Australia. In: Gemstones and Their Origins. Springer, Boston, MA. https://doi.org/10.1007/978-1-4684-6674-4_2
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