What's the difference between crystal, agate, pearl and jade?

Crystal: transparent seasonable is a precious mineral, which can be used to make optical instruments, radio equipment and decorations.

Agate: a fine-grained jade, often mixed with opal, with different colors, or arranged in strips or bands, with black spots or moss-like pearls. In several mollusks, the dense condensate formed by the pearl layer around the foreign particles that are not attached to the shell in or under the film has various shapes, but the most typical one is round and has various colors, but it is generally white or light, with different degrees of luster, and can be used for decoration.