51、金刚石也要琢磨。
Diamond should also be considered.
52、滚动的石头不长苔藓。
Rolling stones don\'t grow moss.
53、爱情是美德的试金石。
Love is the touchstone of virtue.
54、明月松间照，清泉石上来。
The moon shines between pines, and the spring stones come up.
