A stretch bracelet in 8 mm amethyst beads.
The purple took two things to make. Iron caught in the quartz structure as the crystal grew, then natural radiation from the surrounding rock working on that iron over a very long stretch of time. Without both, the same quartz comes out clear.
Keep it out of long spells of direct sun. Sustained UV breaks down the iron centres that produce the colour, and amethyst that fades does not come back. A bracelet gets more sun than a shelf specimen, so this one matters more than it sounds.
Mineral: Amethyst, the purple variety of quartz (SiO₂)
Crystal system: Trigonal
Origin: Not recorded
Hardness: 7 on the Mohs scale; durable for daily wear
Treatment: None
Approx. inner circumference: 7 cm unstretched
Bead diameter: 8 mm
Approx. weight: 15 g
Stringing: Elastic, stretch fit
Photographed as an example. These are strung in batches from the same material, so yours will be closely similar in colour and pattern but not the exact bracelet pictured.