tan duro como una piedra

= as hard as nails, as tough as nuts, as tough as nails, as tough as leather, as tough as old boots, as tough as shoe leather

Ex. From a distance she gives the impression of being as hard as nails.

Ex. Not only was he talented, but he was tough as nuts and rarely has anyone personified grit and determination more than he.

Ex. She was a tough-as-nails realist ready to see the dark side of things.

Ex. Moleskin is a wonderfully comfortable, tough and hard-wearing cotton fabric that is as tough as leather but as soft as velvet to the touch.

Ex. Ferns are as tough as old boots even if the top dies off there is plenty under the ground waiting for the warmer weather so they can erupt.

Ex. Chefs sometimes use the term 'shoemaker' as an insult, implying that the chef in question has made his food as tough as shoe leather.

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= as hard as nails, as tough as nuts, as tough as nails, as tough as leather, as tough as old boots, as tough as shoe leather

Ex: From a distance she gives the impression of being as hard as nails.

Ex: Not only was he talented, but he was tough as nuts and rarely has anyone personified grit and determination more than he.

Ex: She was a tough-as-nails realist ready to see the dark side of things.

Ex: Moleskin is a wonderfully comfortable, tough and hard-wearing cotton fabric that is as tough as leather but as soft as velvet to the touch.

Ex: Ferns are as tough as old boots even if the top dies off there is plenty under the ground waiting for the warmer weather so they can erupt.

Ex: Chefs sometimes use the term 'shoemaker' as an insult, implying that the chef in question has made his food as tough as shoe leather.