Do diamonds cut through glass?

Be warned, however, that these tests may not be very accurate with today's synthetic gemstones. For example, one old adage holds that a real diamond will cut glass, whereas a fake will not. While it's true that diamonds are hard enough to cut glass, some synthetic gems can also scratch glass. read more

Glass is rated a 5.5, and diamonds are a 10. So, genuine diamonds will scratch a mirror. On the other hand, so will quartz (7), moissanite, and cubic zirconia (8). Cubic zirconia engagement rings are almost as hard to scratch as their diamond counterparts. Most well-made synthetic diamonds will seem authentic if you only use the scratch test. read more