Living Spondylus shells are, indeed, very spiny, but the polished product looks very smooth, with some of its color variation strongly resembling that of the Blood Oyster. The resemblance is strong enough that it’s important to ask, when purchasing these materials, if they’re from Blood Oyster or Spiny Oyster. Artists often use Spiny Oyster as a substitute for Blood Coral. Although not nearly as rare as the Blood Coral or Rose Coral, divers collect Spiny Oyster by hand, making the work laborious and relatively expensive, with some risks.
The most commonly used Spondylid Bivalve shell colors include orange, reds, and purples and may include distinct striations and color variations. One also finds pink, red, brown, yellow, orange, and white on the market. The Yellow Spiny Oyster’s especially rare.
In the American Oceans, the Spondylids occur along the North American coasts, as far north as North Carolina, on the Atlantic Coast, and northwestern Mexico, on the Pacific Coast. It develops in waters to South America. The Orange Spiny Oyster occurs in shallow to moderately deep waters, where snorkelers and scuba divers readily harvest them. Purple Spiny Oysters grow in deeper water, making them more difficult to find and harvest.