比喻坚贞不渝的友情close and loyal friendship; friendship as strong as metal and stone

• 使自己和同事、群众成为金石之交，革命友谊深厚如同坚固的金石

  become good friends with one's colleagues and the masses and make revolutionary friendships as deep-seated as strong rocks and metal

• 他们俩朋友有十几年了，关系特别好，可谓金石之交。

  The two of them have been friends for more than ten years. They have a great friendship; one could say that it is as solid as a rock.