Agate, also known as chalcedony, is a type of cryptocrystalline - TopicsExpress



          

Agate, also known as chalcedony, is a type of cryptocrystalline quartz or silicon dioxide. Under unique geological conditions, prehistoric corals and mollusks can fossilize by being replaced with agate from silica-rich ground water percolating through limestone. Of the varieties of fossilized corals found throughout the world, exquisitely detailed specimens from the mountains of× Indonesia are among the most unique. In Indonesia, entire coral heads are often completely preserved and appear just as they did 20 million years ago, though their density is much changed by replacement with silica, iron, manganese and other minerals. There are fern corals, brain corals, hex corals, honeycomb corals and many more.
Posted on: Thu, 09 Oct 2014 00:35:20 +0000

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