The Upratna ("secondary gems") are the traditional alternatives to the nine principal Navratna stones — less costly minerals that the tradition permits in place of the primary gem. They are legitimate articles when sold under their own names. Two things make them worth a laboratory's attention: they are often mislabelled as the principal stone, and they are themselves imitated, since a glass "peridot" is as easy to make as a glass "emerald".
The usual list
Lists vary between texts and practitioners. The commonly cited substitutes are:
| Principal gem | Traditional substitutes |
|---|---|
| Ruby (Manik) | Red garnet, red spinel, rubellite tourmaline, red zircon |
| Pearl (Moti) | Moonstone, white coral, white sapphire in some lists |
| Red coral (Moonga) | Carnelian, red jasper, red agate |
| Emerald (Panna) | Peridot, green tourmaline, green onyx (dyed chalcedony), green jade, aquamarine in some lists |
| Yellow sapphire (Pukhraj) | Citrine, yellow topaz, yellow zircon, heliodor |
| Diamond (Heera) | White sapphire, white zircon, white topaz, rock crystal, opal in some lists |
| Blue sapphire (Neelam) | Amethyst, iolite, blue spinel, lapis lazuli, blue zircon, tanzanite |
| Hessonite (Gomed) | Orange zircon, spessartine garnet, orange agate |
| Cat's eye (Lehsunia) | Quartz cat's eye, apatite cat's eye, tourmaline cat's eye |
What each actually is
Red garnet. Almandine, pyrope or rhodolite; singly refractive, RI 1.74–1.83, SG 3.7–4.3. Inexpensive and durable. Imitated by glass.
Red spinel. RI 1.718, SG 3.60, chromium spectrum. A fine stone, sometimes more valuable than the tradition assumes.
Moonstone. Orthoclase feldspar with adularescence (a floating blue or white sheen). RI 1.52–1.53, SG 2.58. Imitated by opalescent glass and by plastic; the imitation's sheen does not move as the stone is turned the way adularescence does.
Carnelian, red jasper, red agate. Chalcedony, often dyed or heated to improve colour. RI 1.53–1.54, SG 2.60. Dye is common and should be disclosed.
Peridot. Olivine, RI 1.65–1.69 with high birefringence (visible doubling), SG 3.34, iron spectrum. Distinctive; imitated by green glass.
Green tourmaline. RI 1.62–1.64, SG 3.06, strongly pleochroic.
Green onyx. Almost always dyed chalcedony; the name is trade usage. Dye should be stated.
Citrine. Quartz, RI 1.54–1.55, SG 2.65; most citrine is heat-treated amethyst. Citrine vs heat-treated amethyst.
Yellow and white topaz. RI 1.61–1.64, SG 3.53; white topaz is often irradiated and heated to make blue topaz, so untreated white topaz is simple material.
White sapphire. Colourless corundum, often synthetic (flame fusion); RI 1.76–1.77, SG 4.00. Natural white sapphire is less common than the market suggests.
Zircon (all colours). RI over the limit, SG 4.6–4.7, strong doubling, absorption ladder. Natural, often heated to produce blue and colourless. Not to be confused with cubic zirconia, an unrelated synthetic.
Amethyst. Quartz; natural or synthetic (hydrothermal synthetic amethyst is common). Amethyst: natural, synthetic and glass.
Iolite. Cordierite, RI 1.54–1.55, extreme pleochroism.
Lapis lazuli. A rock of lazurite, calcite and pyrite; imitated by dyed jasper and sodalite. Lapis lazuli vs dyed jasper and sodalite.
Quartz and apatite cat's eye. See Cat's eye (Lehsunia).
Why test a substitute
Three reasons. A substitute sold as the principal gem — citrine as pukhraj, garnet as manik — is a mis-sale, and the test catches it. A substitute may itself be glass or plastic, and a buyer paying even a modest sum for a "moonstone" deserves a moonstone. And several substitutes are routinely dyed or heated, which should be disclosed.
The tests are the same as for any gem: RI, SG, polariscope, microscope. How a gemmological laboratory tests a gemstone. For inexpensive articles, a laboratory's identification is quick and the fee proportionate.
Frequently asked questions
Are Upratna "less powerful" than the principal gems?
That is a matter of tradition and belief, outside what a laboratory can test. The laboratory identifies what the stone is.
Which substitutes are most often faked?
Moonstone (opalescent glass), peridot and green tourmaline (green glass), amethyst (synthetic), citrine (heated amethyst, glass), white sapphire (synthetic), and every cat's eye (fibre-optic glass).
Is dyed chalcedony acceptable as a substitute?
Sold as dyed chalcedony, that is for the buyer. Sold as natural green onyx or natural carnelian without disclosure, it is a mis-sale.
Do substitutes need a certain weight?
Traditions often specify weights for substitutes as they do for principal gems. The report gives carats and grams. Ratti, carat and gram.
Is a substitute a worse investment?
Most Upratna are inexpensive and not held for value. Spinel, fine zircon and fine tourmaline are exceptions with markets of their own.