Category Terminology

What is Head Shadow?

HOW DO YOU KNOW IF A GEM IS QUALITY OR NOT?

By Jim Perkins
Copyright 2013

Head shadow may not be a familiar term to everyone that purchases gemstones. This may cause a person to be uncomfortable because they don’t understand the terminology. It is really very simple and I hope this will clarify and make it clear. When gemologists or faceters talk about head shadow they are referring to the shadow our heads cast onto a gem when it is examined close up, approximately 10 inches to 14 inches distance from the viewers eye to the gem. For example: see the illustration:

headshadow1

Here we see a photo of the Pyramids at Giza Egypt. The angle of the viewers head is set at 10°. The light source is behind the viewers head. The pyramids are in front of the viewers head...

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