The theory I heard is that the coral is there because there were normal islands there before (tops of undersea mountains, possibly volcanoes), and the coral grew around them. As the islands eroded (making sand particles), the coral was left behind to form an atoll.
I don't think that sand *has* to be made of anything in particular - calcium will do fine, though it may not last as long.
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chiming
Re: well, yeah...
Date: 2001-01-03 05:55 am (UTC)From:I don't think that sand *has* to be made of anything in particular - calcium will do fine, though it may not last as long.
Maybe Ponti could sort this out for us. ;-)