Review on Enhanced Precision with the Professional Jeweler's Darkfield Loupe: Illuminated Dark Field Hastings Loupe Magnifier by Carla Anderson

Light is the main reason I only give it 4 stars. LED light is sufficient in many cases, but it is rather weak in the red part of the visible spectrum and a magnifying glass is not suitable for an ordinary Maglite as a light source. Visually, this may not pose a problem for you, but light cannot be used effectively as an illumination source for the color filters used to identify specific gems, which you may also want to examine with a darkfield loupe. The instrument has a 1 cm hole for the sample. Anything larger will not fit in the viewport.