Zircon: There are two kinds. One is that natural zircon (tetragonal system) is radioactive and generally not used as jewelry. One is synthetic cubic zirconia, that is, "diamond" is also slightly radioactive, but the synthetic cubic zirconia on the market has been put on the market for more than 1 year, and it will not be put on the market until its radioactivity decays to a harmless degree.

Crystal: divided into artificial crystal and rock crystal, the composition is silicon dioxide, which has a tripartite crystal system, but the value is roughly similar (for large-scale sculpture, it is another way of saying that crystal is developed).

Diamond: Synthetic cubic zirconia.

Semi-precious stone: it is an informal name in the jewelry business, usually imitation stone (stained glass, plastic) or unprocessed gem. It depends.