"Precious" stones include diamonds and rubies. Softer "semi-precious" stones include jade, agate, crystal, opal, garnet, and tiger's-eye.
前者如硬度高而稀有的鑽石、紅寶石、藍寶石、祖母綠等；後者為性質柔和而常見的玉、瑪瑙、水晶、蛋白石、石榴石、虎眼石…… 等數十種。