A stretch bracelet in 8 mm tiger's eye beads, gold and brown, with a band of light that travels across each bead as you move.
That movement is the whole point of the stone. Tiger's eye is built from fibres running parallel through quartz, and each fibre reflects light along its length rather than off a flat surface. Turn your wrist and the reflection travels, because a different row of fibres is catching the light.
It only works with a single light source. Under diffuse daylight or several lamps the effect flattens, which is worth knowing before you decide it looks better in the photos than in your hand.
Mineral: Tiger's eye (a variety name, not an IMA species), quartz (SiO₂) with fibrous riebeckite
Crystal system: Trigonal
Origin: Not recorded
Hardness: 6.5 to 7 on the Mohs scale; hard enough 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.