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Conch:
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Opal:
Conch is a common name that is applied to a number of different medium to large-sized sea snails or their shells. The term generally applies to large snails whose shell has a high spire and a noticeable siphonal canal (in other words, the shell comes to a noticeable point at both ends). Conch jewelry is set with queen conch shells that are precisely cut and polished to the desired design.
Opal is a hydrated amorphous form of silica. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl, and basalt. Precious opal ranges from clear through white, gray, red, orange, yellow, green, blue, magenta, rose, pink, slate, olive, brown, and black. Of these hues, the black opals are the rarest, whereas white and greens are the most common.