Figure 1.
Black stain classifications. (A)–(C) Criteria according to Shourie, (D)–(F) criteria according to Koch et al., and (G)–(I) criteria according to Gasparetto et al.
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.