An LED fibre lamp is a fibre-optic illuminator in which the light source feeding the fibre bundle is an LED rather than a halogen bulb. It produces a bright, controllable beam of cool light at the working tip of one or more flexible gooseneck arms, and is the standard illumination source for the gemmological microscope, where it is used as the primary tool for dark-field, fibre-optic and reflected-light examination of gemstones.

The migration from halogen to LED across the gemmology bench has been gradual but is now near-total. LED sources offer several decisive advantages: minimal heat output at the fibre tip (avoiding thermal shock to heat-sensitive stones such as tanzanite, topaz and certain opals), longer source life (typically tens of thousands of hours against a few hundred for halogen), more stable colour output over the source's life, and lower power consumption. Modern LED fibre lamps offer adjustable colour temperature (commonly 4,000-6,500 K) and dimming, both of which matter when distinguishing colour-shift effects, fluorescence reactions and treatment-related colour features.

For working bench use the lamp's gooseneck arms direct the beam at any chosen angle relative to the stone, allowing dark-field illumination from the side, oblique fibre-optic light for picking up fracture flash effects, and reflected light for surface examination. A typical configuration on a Leica or Gemmoscope bench uses two arms positioned to bring oblique light onto the stone from low angles, with the dark-field stage providing the primary illumination from below.