The Bausch & Lomb Stereo Zoom VII with photo port.

When using a scope, one may readily increase the magnification to more easily detect small defects in a diamond. Before you do this, spend some time under 10x, to avoid possibly being led astray under 30x. Sometimes just the psychological impact of higher magnification can sway one’s judgment, before putting a final clarity grade on a diamond. If you locate an inclusion under 30x, zoom back to 10x and look again for its visibility. If it disappears, it does not count toward the final clarity grade. Only 10x magnification is allowed for clarity grading purposes, this is why a 10x loupe is fine for most diamond merchants to start out with.