A loupe is a small handheld magnifying glass used to see into the interior of a stone. They come in different strengths, with the most common being 10x. Gemologists use loupes to help determine a stone's identity. Faceters use loupes to see inclusions or flaws to help them decide how best to cut a stone. At a gem show, using a loupe incorrectly can mark you as a newbie. I have seen unscrupulous dealer's eyes light up when they see someone using a loupe the wrong way. Getting adept with a loupe takes a little practice, but I am sure you will be handling one like a pro in no time!