6 adjectives to describe durability

It cannot be from the chemical action of the salt water upon the iron, for the flues and other parts of the boiler beneath the water suffer very little from corrosion, and in steam vessels provided with Hall's condensers, which supply the boiler with fresh water, not much increased durability of the boiler has been experienced.

" The other was a great, grey man whom age apparently had not weakened but rather settled and hardened into an ironlike durability; the winds of time or misfortune would have to break that stanch oak before it would bend.

It was raining very heavily, and a dense pall of mist hung low among the pines, giving an impression of melancholy durability.

Among our most useful and valuable trees are the white oak, and its close kin, the red oak, which produce a brown-colored, hard wood of remarkable durability.

They are made of a very hard wood, studded over with pointed flint stones, and fixed by a kind of cement and varnish of surprising durability; the substance being at the same time a strong cement and transparent varnish.

Alcatraz was no starveling mongrel, but to the fierceness of a wild horse and the tireless durability of a mustang he united the subtlety which he had gained in his long battle with the Mexican and above all this, his was the pride of one who had already conquered man.

6 adjectives to describe  durability