PB1 is the highest tier in Lotus Gemology's pigeon blood colour scale for ruby. The designation is reserved for stones that match the laboratory's tightest reference window for the classic Burmese pigeon blood description: a vivid red of medium-strong saturation, with a slight purplish bias under daylight, free of brown or orange modifiers, and showing strong red fluorescence under longwave ultraviolet that reinforces the body colour in mixed lighting.

The reference window

The PB1 designation is calibrated against the laboratory's master colour comparators rather than against any single historical specimen, and the call is made under controlled daylight-equivalent illumination. Lotus has published the parameters of its scale in technical articles, including the position of PB1 relative to PB2 and PB3 along axes of hue, saturation and tone, allowing dealers and appraisers to calibrate their own colour reading against the scale.

Trade significance

A PB1 stone is, in commercial terms, at the apex of the laboratory's colour grading and trades at material premiums to PB2 stones of equivalent size and clarity. A PB1 call alone does not guarantee Burmese origin, and a Mozambican stone meeting the colour parameters can earn a PB1 designation; nonetheless, the most expensive PB1 stones in the market are almost always Burmese unheated rubies, where the colour designation, the unheated status, and the origin combine to produce a stone in the highest possible price band.

Reading a PB1 report

Buyers should read a PB1 designation alongside the laboratory's complete report. Treatment status (H, H(a), H(b), H(c) or unheated), origin determination, weight, clarity grade, and inclusion characterisation all bear on price; PB1 is the colour element of a fuller picture rather than a standalone grade.