The pearl, with its magnificent color and graceful character, China is the country that discovers and uses the pearl in the world earliest that praised as " gem queen ". The pearl produced by sand grain or small worm entering into mussel body, stimulate its covering membrane, and produce pearl texture, all these condition can come into being gradually.
   Chemical composition : Calcium carbonic, about 82-86% of Ca [CO3 ] in the composition , pearl cutin is 10-14%, water 2%, this percentage is not too fixed to change .
Shape : Orthogonal and brilliant, the small crystal is radial, have concentric layer of structure.
Color: Color of pearl divide two kinds of , those are texture color and colorful, color of pearl being formed by pearl layer to whom ray radiation, texture color as following: White pearls with white texture on which presenting white, milk color, color of bright milk, bright orange, bright rosiness and also take on pink.
   Physical property: Pearl gloss . opacity and even semitransparently, hardness 2. 5-4. 5 proportion 2. 6-2. 78, propagated artificially are 2. 72-2. 78.

Produce and divide into different type:
Sea pearl : Pearl which the pearl shell produced naturally in the sea water.
Fresh water pearl : The pearl which the pearl shell produced naturally in the fresh water, means exclusively that the pearl in the river.
Lake pearl : The pearl which the pearl shell produced naturally in the lake water, also actually is fresh water pearl.
Cultured pearls: Pearl that the artificial cultured.
Texture color is divided:
White pearl: The basic color is the white on this basis can appear all sorts of pearl glosses while being getting white.
Black pearl : The basic color is the black on this basis can appear all sorts of pearl glosses while being getting dark.
Variegated pearl : The color of the texture is not white , not black, but other colors, Also called " the coloured pearl ".