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.
Rutile is a mineral composed primarily of titanium dioxide. Rutile has among the highest refractive indices at visible wavelengths of any known crystal, and also exhibits a particularly large birefringence and high dispersion. Small rutile needles present in gems are responsible for an optical phenomenon known as asterism. Asteriated gems are known as "star" gems. Star sapphires, star rubies, and other "star" gems are highly sought after and are generally more valuable than their normal counterparts.