Talk:Amethyst/@comment-27604741-20160210192610/@comment-5544341-20160324133001

Quartz is one of the most abundant and diverse minerals on earth. In its plain form, it's just a clear gem with physical imperfections that appear white. But it can also be pink, in which case it's rose quartz. Or it can be purple, in which case it's amethyst. It can be orange, in which case it's citrine. It can also have a grayish-brown color, making it smoky quartz.

But that's just macrocrystalline quartz, when it's microcrystalline (meaning it's a lot of tiny crystals that are smaller than you can see connected as a single stone), it's opaque, and known as chalcedony. Chalcedony has forms like agate, aventurine, carnelian, bloodstone, and onyx. Rose, Amethyst, and Jasper were all listed as "Quartz type" in Guide to the Crystal Gems.

But they're all still made of the mineral Quartz.

On the other hand, Pearls do not have variations like this. They're made biopolymers and a mineral called aragonite; together this substance is known as "mother of pearl".

Peridots are made from a mineral called olivine, but as olivine is not the gem name, her gem type is simply "Peridot".

Lapis Lazuli is mostly made from a blue mineral called lazurite, but again, lapis lazuli is the name of a gem that the mineral forms, so she's a Lapis lazuli type.

Rubies and sapphires are both made from aluminium oxide, and are also known as corrundum, thus if they had entires included in the Guide to the Crystal Gems, they might've been classified with the gem type Corundum, despite the differences we see in how each is treated.

And that's why the quartzes are listed as Quartzes.