Jade
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A Jade is a kind of stone. We use the name "jade" for two different sorts of mineral. The first sort is nephrite. This is a form of actinolite (asbestos is a sort of actinolite, too). The second sort is the mineral jadeite, and it is a pyroxene.
Nephrite is Ca2(Mg, Fe)5Si8O22(OH)2.
Jadeite is NaAlSi2O6.
The two sorts of jade look nearly the same. People only found that they were two different sorts in 1863. Jade is very hard. In the past, people used it to make knives and weapons. Later, when people could use metals, they liked jade because it looked good. Today people also use jade for jewellery.