The everyday word for a stone or rock
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petrify
turn to stone
Piedra means stone and is related to the English word petrify0, which means to turn to stone.
piedra

stone, rock
A piece of hard mineral: a stone, a rock.
Tropecé con una piedra en el caminoI tripped on a stone on the path
Los niños lanzaban piedras al ríoThe kids were throwing rocks into the river

stone (medical)
A hard mineral lump that forms inside the body (e.g. a kidney stone or gallbladder stone).
El médico le encontró una piedra en el riñónThe doctor found a stone in his kidney
Las piedras en la vesícula pueden ser dolorosasStones in the gallbladder can be painful
piedra preciosa

gemstone, precious stone
Literally a precious stone, like a gem.
El anillo tenía una piedra preciosa en el centroThe ring had a gemstone in the center
Compró una piedra preciosa muy raraShe bought a very rare precious stone