Flint
Deuteronomy 8:15: Who led thee through that great and terrible wilderness, wherein were fiery serpents, and scorpions, and drought, where there was no water; who brought thee forth water out of the rock of flint;
Psalm 114: 8: Which turned the rock into a standing water, the flint into a fountain of waters.
Isaiah 50:7: For the Lord GOD will help me; therefore shall I not be confounded: therefore have I set my face like a flint, and I know that I shall not be ashamed.
Literal Hebrew translations from Strong's for the above three verses:
flint, rock
Isaiah 5:28: Whose arrows are sharp, and all their bows bent, their horses' hoofs shall be counted like flint, and their wheels like a whirlwind:
Literal Hebrew translations from Strong's for the above verse:
narrow, tight
straits, distress
adversary, foe, enemy, oppressor
hard pebble, flint
Ezekiel 3:9: As an adamant harder than flint have I made thy forehead: fear them not, neither be dismayed at their looks, though they be a rebellious house.
Literal Hebrew translations from Strong's for the above verse:
flint, hard pebble
used as a knife