Minerals are naturally-occurring in the earth's crust. Technically, a gemstone is supposed to be a piece of mineral crystal, but the definition has changed over time to include a few other things (but sometimes rocks) . Amber occurs in trees and, while it's a gemstone, it cannot be classified as a mineral. Pearl is an organic gemstone.
Gemstones are used for aesthetic purposes to make jewelry or ornaments. The term is getting more confusing due to the creation of lab-made gemstones.
The gemstones are the prettiest minerals cut specifically to make jewelry.
Minerals actually have their own classification system: color, form, luster, streak, hardness, cleavageandfracture.
Gemstones are usually measured by their hardness, size, and rarity. Unpolished gemstones simply look like ordinary rocks; cutting and polishing allows them to have brilliance and sometimes color (leading to their value) that can't be found in other types of stones. Gemstones are usually classified as semiprecious and precious stones.
Some semiprecious gemstones include amethyst, garnet, citrine, turquoise, and opal.
Precious gemstones include diamond, emerald, ruby, and sapphire.