冰晶（英语：Diamond dust）是一种能在地面附近观测到的微小冰块。因为英语的关系，亦有人称作「钻石尘」或「钻石星尘」。

这些小冰块经常出现在逆温时期，热空气与冷空气混合的时候。尽管冰晶可能在任何地方被观测到，但它最常见的出现地点是南极洲，在那里它几乎是全年出现。

冰晶与雾非常相似，但是雾是由小水珠构成的，而冰晶是由微小冰块所形成。另外，如果出现雾，那幺能见度将会大大降低，但冰晶一般情况下非常小所以不会对能见度造成太大的影响。

Diamond dust is a ground-level cloud composed of tiny ice crystals. This meteorological phenomenon is also referred to simply as ice crystals and is reported in the METAR code as IC. Diamond dust generally forms under otherwise clear or nearly clear skies, so it is sometimes referred to as clear-sky precipitation. It is most commonly observed in Antarctica and the Arctic, but it can occur anywhere with a temperature well below freezing. In polar regions diamond dust may continue for several days without interruption.