'Flint' in the Bible

But Zipporah took a flint [knife], and she cut off the foreskin of her son, and she touched his feet, and she said, "Yes, you [are] a bridegroom of blood to me."

the one leading you in the great and terrible desert [infested] with {dangerous} snakes and scorpions and parched ground, where there is no water, [and] the one bringing out water for you from flint rock,

At that time Yahweh said to Joshua, "Make for yourself knives of flint, and circumcise the {Israelites} a second time."

So Joshua made knives of flint, and he circumcised the {Israelites} at the hill of the foreskins.

Whose arrows are sharp, and all of his bows are bent. The hoofs of his horses are reckoned like flint, and his wheels like the storm wind.

And the Lord Yahweh helps me, therefore I have not been put to shame; therefore I have set my face like flint. And I know that I shall not be ashamed;

Like a diamond {harder than flint} I have made your forehead; you must not fear them, and you must not be dismayed {on account of them}, for they {are a rebellious house}.