Birch grows around the world primarily in the Norhtern Hemisphere and at higher altitudes. There are so many types of Birch and they all seem to be capable of being figured. It seems that karelian and Masur Birch are one in the same. I am guessing that the name Masur originated in North America and that Karelian originated in Europe. If any one knows the truth to that feel free to contact me. Ice Birch, Flame Birch, Curly Birch and Karelian/Masur Birch (Birch Burl) are believed to be the result of grain deviations possibly due to the larvae of burrowing insects that create pith flecks which show as irregular dark markings and local grain disturbance. Over the years we have made many Ice Birch and karelian Birch panels,doors,component parts, fixtures and cabinets and I do not remember anything that didn't look good. As a result we pretty much always have Karelian and Ice Birch in our inventory.