Masur Birch is not a particular species of birch, but is rather a grain figure that is most commonly seen in Downy Birch and Silver Birch. It is also sometimes known as Karelian Birch—with Karelia being a region between Finland and Russia. Once surmised to have been caused by the boring larvae of a certain beetle, Masur Birch in Norway has been shown to be hereditary, classifying the name of the variant as Betula pendula var. Carelica. Regardless of the exact cause and makeup of the peculiar grain pattern, the resulting figure and appearance is very similar to burl wood or birdseye maple, though of a different origin. Masur Birch is commonly used for turned objects, decorative veneer, knife handles, and other small specialty items.
A special thanks to Steve Earis for providing the wood sample and turned photo of this wood species.