"A deposit of interlocking ice crystals (hoar crystals) formed by direct sublimation on objects, usually those of small diameter freely exposed to the air, such as tree branches, plant stems and leaf edges, wires, poles, etc., which surface is sufficiently cooled, mostly by nocturnal radiation, to cause the direct sublimation of the water vapor contained in the ambient air."
Of course this is a superb definition. But it does not tell you anything about beauty. For that, you need your eyes and brain and all that you have ever learned and felt. And all I can do is share this photo (click on the photo to see it in a larger size) with you, and tell you that it was magnificent. (Sax-Zim Bog, St. Louis County, MN; Feb. 24, 2008).