Fluorite crystals on calcite crystals. Fluorite crystals measure up to 3mm and fluoresce a beautiful purple colour under our longwave UV light. The calcite crystals fluoresce orange under one longwave UV light and pink under another longwave UV light. UV responses can differ depending on the strength of the torch and/or the wavelength used. Readily available “Blacklight” torches are usually about 405 nanometres (nm) whereas true longwave wavelength is 365nm. Specimen measures approx. 30 x 40mm.