Masur Birch is not a distinct species of birch but a highly decorative figured grain variation, most commonly occurring in Silver Birch and Downy Birch. It is also widely known as Karelian Birch, named after the Karelia region between Finland and Russia, where this distinctive figure has historically been cultivated and prized.

The figure is characterised by dense clusters of small dark flecks and irregular markings set within a pale, creamy to lightly pinkish ground. These markings are caused by abnormal growth, where small sections of bark or dormant buds become engulfed by the expanding wood fibres. Earlier theories attributed the figure to insect activity, but research has shown that the condition is hereditary in some populations, often classified botanically as Betula pendula var. carelica.

Visually, Masur Birch shares similarities with birdseye maple and certain burr woods, though the structure and origin of the figure are entirely different. The grain produces a striking three dimensional effect when polished, making it particularly suited to fine decorative work. Because the figured areas occur unpredictably and in limited sizes, the wood is rarely available in large sections and is most often encountered as veneer or in smaller solid pieces.

Historically, Masur Birch has been used for turned objects, knife handles, boxes, decorative veneers, and other refined items where its distinctive figure could be fully appreciated.