Tourmaline is a semi-precious gemstone that comes in a wide range of colors, from black to brown, pink to green, and blue to red. It is a complex borosilicate mineral that is formed in metamorphic rocks and can also be found in igneous rocks and alluvial deposits.

Some of the most popular varieties of tourmaline include:

• Rubellite: This is a pink to red tourmaline that is often considered to be the most valuable and sought-after variety.

• Paraiba: This is a rare and highly prized type of tourmaline that comes in a bright blue-green color. It is named after the Brazilian state where it was first discovered.

• Watermelon: This type of tourmaline is green on the outside and pink on the inside, giving it a distinctive "watermelon" appearance.

• Indicolite: This is a blue tourmaline that can range in color from light to dark blue.