'Breastplates' in the Bible

and they had breastplates as breastplates of iron, and the noise of their wings is as the noise of chariots of many horses running to battle;

And thus I saw the horses in the vision, and those sitting upon them, having breastplates of fire, and jacinth, and brimstone; and the heads of the horses are as heads of lions, and out of their mouths proceedeth fire, and smoke, and brimstone;