A stretch bracelet in 8 mm beads of clear quartz shot through with black tourmaline.
The black needles grew first. Tourmaline crystallised as slender rods, and quartz formed around and through them afterwards, sealing them inside while they were still intact. Each bead is a slice through that, which is why the needle pattern is different on every one and why some catch the light through the quartz and others sit solid.
Two minerals, two hardnesses, one bead. The quartz is the harder of the two, so the tourmaline needles are the part that will show wear first.
Mineral: Quartz (SiO₂) with black tourmaline, schorl
Crystal system: Quartz trigonal, tourmaline trigonal
Origin: Not recorded
Hardness: Quartz 7 on the Mohs scale, schorl 7 to 7.5; 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.