The spark processing of metallic Sn yields a powder, which is a mixture of nanosize Sn and crystalline SnO2. This paper reports the characteristics of nanosize Sn powders. Scanning tunneling microscopy (STM) and transmission electron microscopy (TEM) studies reveal an existence of spherical shaped nanocrystals ranging from 2 to 5 nm in size. In contrast the measured surface area of spark processed Sn (sp-Sn) powders by BET is 27.7 m2/g and calculated average size of sp- Sn is about 31 nm, which is close to one order of magnitude larger than the observed size. Further, the characteristics of sp-Sn powders are studied by Raman, and differential thermal analysis (DTA).