"Tourmaline" is the name of a large group of boron silicate minerals. These minerals share a common crystal structure and similar physical properties - but vary tremendously in chemical composition. The wide range of compositions and color zoning within crystals causes tourmaline to occur in more colors and color combinations than any other mineral group.
Tourmaline is one of the world's most popular gemstones and it serves as a birthstone for the month of October. Because of its popularity, tourmaline is easy to find in jewelry stores. Well-formed tourmaline crystals are also valued by mineral specimen collectors. Specimens with attractive colors and crystal forms can sell for thousands of dollars.

to read more please visit  (geology.com)

please note that the colours have not been edited however they are under high power lights to show the colour, there are 2 types of photos, one using the phone flash (usually crystals that are easier to see the colours) and the other us using an external high power light source (usually crystals that are harder to show the colours using phone alone, either due to the play of colours of the phone showing the crystal looking very different to the crystal. we have tried to make sure the photos look like the actual crystal however as mentioned above they are taken under high power lighting and zoom so may vary compared to what is seen with the naked eye.

All sizes shown are in mm
​text updated at 12.16 20/09/2021
Other (black, clear, orange or purple)
Watermelon
Turquoise
Pink
Green

Tourmaline