Lapis lazuli is one of the oldest gem materials in human use — the blue of ancient Egyptian jewellery and Renaissance ultramarine pigment. It is a rock composed mainly of the blue mineral lazurite with variable amounts of white calcite and brassy pyrite. Fine lapis is deep, even blue with sparse pyrite and little calcite; most commercial lapis is paler, more calcite-streaked, and — often — dyed to deepen the blue. Imitations are common and, at the low end, dominant.
What lapis lazuli is
An aggregate rock. Properties: SG 2.7–2.9 (varies with pyrite and calcite content), hardness 5–5.5, RI about 1.50 (spot reading, of limited use), opaque, inert under long-wave UV (calcite patches may glow pink or orange under long-wave; lazurite is inert), with the characteristic combination of blue lazurite, white calcite and metallic gold pyrite in a granular texture.
What is sold as lapis
Dyed jasper ("Swiss lapis", "German lapis"). Jasper (opaque chalcedony) dyed blue. Uniform colour with no pyrite; or with imitation "pyrite" as gold-coloured flecks that are not metallic under magnification; dye in fractures; SG 2.6. Acetone may lift dye. The commonest imitation.
Sodalite. A natural blue mineral, related to lazurite, that occurs in massive form and is sometimes sold as lapis. Sodalite is usually a more violet or greyer blue, has white veining but no pyrite, and fluoresces orange under long-wave UV in patches. SG 2.2–2.3 — noticeably lighter than lapis. A legitimate stone under its own name.
Reconstituted lapis. Lapis powder bound with resin, sometimes with added pyrite flakes. Uniform texture, resin fluorescence, no natural calcite veins.
Dyed howlite and magnesite. As for turquoise; dyed blue rather than turquoise-blue. Veined, soft, dye at the drill hole.
Glass and plastic. With gold flecks added; bubbles, warmth, seams.
Gilson synthetic lapis. A manufactured lazurite-like material with added pyrite; uniform, lacks calcite, lower SG, and porous — absorbs water.
Treatments of genuine lapis
Dyeing. Common, to deepen pale blue and mask calcite; dye concentrates in the calcite (which is more porous) and shows as blue-tinged white areas, in fractures and at the drill hole. Acetone swab lifts some dyes. Disclosed on a careful report.
Waxing and resin impregnation. To improve polish and stabilise; detected under UV and at the surface.
How the laboratory examines lapis
Magnification is the key test: the granular blue-white-gold texture with genuinely metallic pyrite identifies lapis; uniform blue with painted flecks identifies dyed jasper; absence of pyrite with violet-blue and orange UV patches identifies sodalite. SG supports (2.8 lapis; 2.6 jasper; 2.25 sodalite). UV shows calcite, sodalite and resin. Dye is checked at the drill hole and in calcite areas. Report states: natural lapis lazuli (dyed or not), or the actual material.
Frequently asked questions
Does real lapis always have gold flecks?
Nearly always some pyrite is present; the finest grades have very little. A stone with no pyrite at all should be checked against sodalite and dyed jasper.
Is sodalite fake lapis?
Sodalite is a genuine mineral and a fine blue stone. It is a mis-sale only when sold as lapis.
Is dyed lapis real lapis?
It is genuine lapis with enhanced colour. Both facts should be stated.
Why does my lapis have white patches?
Calcite is a natural component of the rock. Heavy calcite lowers the grade; it does not affect identity.
Can lapis be tested without damage?
Yes — magnification, SG and UV are all non-destructive. The solvent swab, if used, is applied to an inconspicuous spot.