Shwetark Ganesh is a naturally occurring Ganesh Murti from the stem of Shwetark tree. The white stem on aak tree is very rare. When an aak tree has a white stem it is known as Shwetark (Shweta 
means white).
means white).
The shape of the step of Shwetark tree is similar to Lord Ganesha.
Naturally occurring Shwetark Ganesh idols are very rare and it falls under the category of Swayambhu Ganesh idols.
The popular belief is that if one worships Shwetark Ganesh he will be blessed with financial prosperity, peace and good health.