Prismad

Prismad is a gemstone colour-change bench for gemologists, dealers, and collectors. Select a stone, choose two light sources, and watch computed sRGB swatches update in real time — a full radiometric simulation of how light travels through a gem, running entirely on-device with no account required. The Bench is the heart of Prismad. Pair any of 12 gem species — from Alexandrite to Tanzanite — with two of 8 named illuminants, from a midday window to a tungsten bulb or UV lamp. Adjust path length to match the depth of your stone, then read the result: two calibrated colour swatches, a CIE delta-E colour difference value, hue shift in degrees, tone, saturation, and a plain-language verdict — None, Weak, Distinct, or Dramatic. A sparkline shows how colour difference deepens as path length grows. The Pair screen turns your camera into a measurement instrument. Photograph the same stone under two different lights, sample each photo with a draggable reticle, and compare the measured colour pair against the Bench prediction side by side. A grey-card tap white-balances each reading for field-quality results anywhere. The Catalogue gives you the full reference layer: absorption bands, refractive indices, pleochroism axes, and spectral profiles for every stone and lamp in the app, plus plain-language explanations of six optical phenomena — colour change, pleochroism, zoning, extinction, windowing, and fluorescence. Readings are saved with their complete data and optional photo pair, so you build a personal log of every stone that crosses your bench. No subscription, no network, no account — just the bench.