Three threes in smoky quartz

The same puzzle as our wooden piece of the same name, with every part cut from smoky quartz instead. Each part is shaped from one piece of stone and polished, and every edge and corner is rounded so the stone does not chip where the cord pulls across it.

Smoky quartz is quartz in a deep espresso brown. At 7 on the hardness scale it is harder than a steel knife, so everyday use does not scratch it.

Smoky quartz grows as large quartz crystals rather than tiny locked grains. It takes a glassy polish, but it is more brittle than jasper or onyx and a hard knock can chip an edge, so treat it like fine glass.

The cord is the same as on the wooden piece, so the solution is the same. The piece comes in nine stones and their natural colours: pick one above and the price follows it.