Every serious gold prospector needs a magnifier in their kit. This loupe features a polished glass 10X lens in a tough plastic and metal housing. This glass portion of this 10 power loupe is 15mm (0.59 inch) diameter.

Some people do not use a jewelers lens properly, holding it far away like a magnifying glass. This reduces the area seen and distorts the image. The proper way to use a loupe is to hold it close to the eye, bringing the item to be seen up to the lens to achieve proper focus. This is ideal for examining rocks and ore samples for enclosed gold and other minerals, but not as handy for looking at material in the bottom of a gold pan. For that you probably want a standard magnifying glass. See the attached video for a better idea on the proper use of a jewelers loupe.