How to tell if lapis lazuli is real
For collectors: look first, weigh second, then ask a lab. Three of five named lapis imitations weigh inside GIA’s range; one glass nearly matched lazurite.
To tell if lapis lazuli is real, look at the white and gold under a 10x lens, weigh it in water, then use a laboratory. GIA gives lapis specific gravity 2.75 ± 0.25. Dyed jasper, dyed calcite marble and dyed howlite all weigh inside that range, and a 1983 glass came within 0.003 of lazurite's density.
In short
- Lapis is a rock, so it has no single set of numbers. The GIA lapis lazuli page calls it an aggregate of several minerals, mainly lazurite, calcite and pyrite, with specific gravity 2.75 (+/- 0.25). The Handbook lazurite sheet gives the blue mineral hardness 5 to 5.5, density 2.38 to 2.45 and a bright blue streak. Why lapis outweighs lazurite is worked on is lapis lazuli a mineral or a rock and not repeated here.
- The 3-of-5 window. GIA’s range is 2.50 to 3.00: a 20.00 g piece reads 12.00 to 13.33 g in water. Of the five imitations the International Gem Society lapis lazuli article and GIA name that have a published density, three fall wholly inside it: dyed jasper sold as “Swiss lapis” (12.16 to 13.13 g), dyed calcite marble (12.62 g) and dyed howlite (12.09 to 12.28 g). A lapis-range reading does not pass a stone.
- The near-match glass. Bosshart (Gems & Gemology, Winter 1983) tested 8 mm beads sold as “blue quartz from India”: a cobalt glass with density 2.453, index 1.508 and hardness about 5½. Lazurite’s sheet gives 2.38 to 2.45, 1.502 to 1.522 and 5 to 5.5. In water the glass reads 11.85 g, 0.01 g from lazurite’s 11.84 g. What exposed it was a lens: white cristobalite in fern-like and radiating patterns, and no pyrite.
- Documented failure: the swab. GIA’s Summer 1989 lab notes record 68 beads sold as lapis that were dyed calcite marble. An acetone-soaked swab produced no stain; a swab with 10% hydrochloric acid came away light blue. The Summer 1986 notes record dyed lapis sealed with paraffin that made the swab test less revealing. A clean swab does not clear a stone.
- Finish state. Write one of three things on the label: consistent with lapis, treatment unknown; a named imitation; or needs a laboratory. The IGS says acid and streak tests on lapis are destructive and for a professional gemmologist only, so this page does not offer them. Dye checks in general are on how to tell if a crystal is dyed.
| Material | Named as a lapis imitation by | Density (source) | 20.00 g piece in water | Inside GIA’s lapis range, 12.00 to 13.33 g? | What exposed it in the documented case |
|---|---|---|---|---|---|
| Lapis lazuli | — | 2.75 ± 0.25, so 2.50 to 3.00 (GIA) | 12.00 to 13.33 g | The range itself | — |
| Lazurite, the mineral alone | — | 2.38 to 2.45 (Handbook) | 11.60 to 11.84 g | No: below | — |
| Dyed jasper, “Swiss lapis” | IGS; GIA 1989 (43 beads) | 2.55 to 2.91 (IGS jasper) | 12.16 to 13.13 g | Yes, wholly | Refractive index and appearance eliminated lapis; X-ray transparency separated it from dyed calcite (GIA 1989) |
| Dyed calcite marble | GIA 1989 (68 beads; 21 more in a second strand) | 2.7102 (Handbook calcite) | 12.62 g | Yes | A chip at the drill hole showed shallow dye and pale yellow calcite; 10% HCl effervescence; X-ray diffraction (GIA 1989) |
| Dyed howlite | IGS | 2.53 to 2.59 (Handbook howlite) | 12.09 to 12.28 g | Yes, wholly | No laboratory case fetched; hardness 3.5 on its sheet |
| Cobalt glass, “blue quartz from India” | Bosshart 1983 | 2.453, one specimen (Bosshart) | 11.85 g | No: below, 0.01 g from pure lazurite | White cristobalite patterns under slight magnification; no pyrite (Bosshart) |
| Sodalite | IGS: the one convincing natural simulant | 2.27 to 2.33 (Handbook) | 11.19 to 11.42 g | No: below | IGS: no pyrite inclusions |
| Enamel, plastic; synthetic lapis (Gilson, Chatham) | IGS | No density in the fetched sources | Not worked | Not known | Not documented in the fetched sources |
How do I tell if my lapis lazuli is real? The five steps
Lapis lazuli is tested in five steps, and the honest finish is often “needs a laboratory”. Day one needs a 10x lens, a strong side light and a 0.01 g scale. The sequence, with what each step can and cannot decide:
1. Name the white and the gold. GIA lists lazurite, calcite and pyrite as lapis’s three major minerals; the IGS says the white is calcite and the brassy gold pyrite. The International Gem Society sodalite article says sodalite can be told from lapis by its lack of pyrite, and Bosshart’s glass had no pyrite grains. Gold flecks do not prove lapis, though: Bosshart cites Nassau (1980) for a lapis imitation made of a blue glass containing copper crystals.
2. Look at the drill hole and the cracks. GIA’s 1986 notes say dye in lapis has been found primarily in cracks and porous areas. In the 1989 case a chip near a drill hole showed how shallow the dye went and the material’s true pale yellow colour. The general method is on how to tell if a crystal is dyed.
3. Weigh it in water. A 20.00 g piece of lapis reads 12.00 to 13.33 g on GIA’s figures; the method is on how to measure specific gravity at home. Read the result against the table: a reading in the window clears nothing, and a reading below it fits pure lazurite as well as glass or sodalite.
4. Ask in writing whether the piece is dyed, waxed or oiled: the IGS lists dyeing (common), heat treatment, fracture filling, and wax and oil impregnation as lapis treatments. 5. Send it out if the answer matters. The tests that settled the documented cases were refractive index, X-ray transparency, a thermal reaction tester, X-ray diffraction and spectroscopy, all laboratory work.
Does weighing prove lapis is real? The 3-of-5 window
A scale cannot pass a piece of lapis: three of the five named imitations with a published density weigh inside GIA’s lapis range. GIA gives 2.75 (+/- 0.25), so 2.50 to 3.00, and a 20.00 g piece reads 12.00 to 13.33 g in water. Worked as 20 − 20/D, dyed jasper reads 12.16 to 13.13 g on the International Gem Society jasper article’s 2.55 to 2.91; dyed calcite marble reads 12.62 g on the calcite sheet’s 2.7102; dyed howlite reads 12.09 to 12.28 g on the Handbook howlite sheet’s 2.53 to 2.59. All three ranges sit wholly inside the window.
Below the window is not a verdict either. The two named imitations that fall below it, Bosshart’s glass at 11.85 g and sodalite at 11.19 to 11.42 g, keep company with lapis’s own blue mineral: pure lazurite reads 11.60 to 11.84 g. The IGS gives pure lapis 2.38 to 2.45 and gem lapis 2.7 to 2.9, or higher if much pyrite is present, so a light reading can mean lazurite-rich material as easily as an imitation.
What the scale is for. It records a number that a laboratory can use, and it flags a reading far outside every row. The enamel, plastic and synthetic lapis the IGS names have no density in the sources fetched for this page, so they are not placed on the scale. Hardness separates some of them, jasper at 7 on the IGS figure and howlite at 3.5 and calcite at 3 on their sheets against 5 to 6 for lapis on the IGS figure, but lapis itself contains calcite, so one soft spot proves nothing, and the test marks the piece; the method is on how to test mineral hardness properly.
The glass that nearly matched lazurite three ways: a documented failure
A 1983 cobalt glass fell inside lazurite’s ranges for refractive index and hardness and 0.003 above its density, and was exposed by what a lens showed inside it. George Bosshart, then laboratory director of SSEF in Zurich, examined a necklace of 8 mm violet-blue beads offered as “blue quartz from India”. His table gives specific gravity 2.453 on one specimen, refractive index 1.508, Mohs hardness approximately 5½, streak white, and no reaction to diluted HCl.
Against the lazurite sheet. The sheet gives density 2.38 to 2.45, index n = 1.502 to 1.522, hardness 5 to 5.5. The glass’s index sits inside lazurite’s range, its hardness inside lazurite’s, and its density 0.003 above lazurite’s top value: 11.85 g in water for a 20.00 g piece against 11.84 g, one step on a 0.01 g balance. Bosshart notes the index did not differ markedly from lapis (approximately 1.50), while the density was significantly lower than the average for lapis (approximately 2.80).
What did separate it. The beads showed a tinge of violet beyond top-quality lapis and contained no pyrite grains. Under magnification the white was not calcite but crystallites of low-cristobalite in fern-like and radiating patterns, which Bosshart calls the most diagnostic gemmological property, with spectrophotometry, X-ray fluorescence and X-ray diffraction confirming it. He called it the best glass imitation of lapis he had seen to date. The lesson for a collector is the order of the steps: the lens comes first, because the numbers all but matched.
Will acetone show if lapis is dyed? What GIA’s lab notes record
An acetone swab can come away clean from dyed material sold as lapis, so a clean swab does not clear a stone. GIA’s West Coast laboratory, in the Summer 1989 lab notes, examined a strand of 68 opaque blue beads of about 10.4 mm sold as lapis lazuli. They were inert under long- and short-wave UV, gave vague spot indices of about 1.4 to 1.6 with a blink suggesting a carbonate, and effervesced with a tiny droplet of 10% HCl. An acetone-soaked swab produced no stain; a 10% HCl solution on the swab gave a light blue one. X-ray diffraction matched calcite: dyed calcite marble.
A mixed strand, the same issue. A necklace whose owner complained it stained her skin proved to hold 21 beads of dyed calcite and 43 of “Swiss lapis”, dyed jasper. The lack of UV fluorescence suggested dye; refractive index and appearance eliminated lapis; X-ray transparency separated the two imitations, the calcite showing whiter.
Wax hides dye. The Summer 1986 notes describe lapis that was dyed and then “sealed” with oil, wax or paraffin. On one heavily dyed strand of 7 mm beads the swab test was not as revealing as on earlier stones; a thermal reaction tester showed paraffin, and under short-wave UV only about half the beads showed the chalky green fluorescence the notes call characteristic of natural lapis. These are laboratory observations, reported as such; GIA calls the dilute-acid carbonate test destructive, to be done only in an inconspicuous area under magnification, which is why this page does not offer it. The identification questions are indexed at the collecting guides. Nothing on this site is offered for sale; the wanted list is the only commercial route.