The, divers, the, Gulf, in, One, descended, a, weighted, a stone,, a, nose, and, a, for, oysters., the bottom,, 10–15 metres,, worked, fast, possible, often, more, two, , shells, the, was, and, ascended., good, might, fifty, a, The, was seasonal,, from, to September,, the, waters, the, allowed, For centuries,, natural, beds, Bahrain, Qatar,, the, States, the, natural, in, world:, Basra pearl,, for, trading, where, were, and sold,, the, against, all, pearls, measured., quality, the, of, specific, conditions, the, temperature, salinity,, the, diet, to, molluscs, a, quality, lustre, was, to, experienced, merchant., trade, abruptly, the 1930s,, by, simultaneous, the, Depression, demand, luxury goods,, the, of, cultured, destroyed, price, for, natural, pearls, had, the, economy, millennia.
Quick, what, a pearl? A, is, biomineralised, formed, molluscs (primarily, oysters, the, genus, various, mussels), the, tissue, nacre, an, Nacre, of, platelets, aragonite (a, of, carbonate, CaCO₃), by, organic, matrix, conchiolin., thin-film, of, in, nacre, produces, optical, called, or, Natural, form, without, intervention., pearls, produced, inserting, nucleus (usually, shell, or, tissue), the, to, nacre, Sources:, Gem, Guide (2006),, 70–81; Wise, R.W.,, of, Gem, (2016),, 216–240;, Pearl Research.

Nacre, how, mollusc, the gem

When, irritant, the, tissue, a mollusc,, mantle, respond, secreting, around, irritant,, encasing, in, after, of, same, used, build, shell's, surface., nacre, deposited, flat, platelets, aragonite,, 0.3–0.5, thick, 5–15, in diameter,, in, brick-wall, and, by, thin, of, protein (conchiolin)., platelet, a, crystal, aragonite, with, flat, parallel, the pearl's, The, of, of, thin, layers, what, both, hardness, nacre (harder, the, aragonite, alone, to, composite structure), the, effect, makes, unique (GIA, Reference Guide, 2006,, 70–71; Wise, 2016).

The, of, nacre, varies, pearl, and, conditions., pearl, layers, typically, thick, a, nucleus, approximately, South, pearl, is, 2–6mm, Natural pearls,, entirely, nacre, no nucleus,, nacre, (GIA;, Pearl, Book).

Lustre, why, glows

Pearl, is, by, interference:, same, phenomenon, produces, colours, a, bubble, an, film, water., light, a, layer,, is, from, top, and, passes, to, reflected, the, layer, The, reflected, travel, different, lengths, reaching, eye., the, difference, a, wavelength, light,, wavelength, reinforced (constructive interference);, it, a half-wavelength,, is, (destructive interference)., result, a, enhancement, certain, that, with, viewing angle,, the, glow, seems, come, inside, pearl, than, its, (Nassau, K.,, GIA, Reference Guide, 2006).

Pearl, stacked, platelets, thin-film interference Nacre, (schematic) Aragonite, ~0.4μm thick Organic, between layers Thin-film, → lustre Incident light Two, beams different, lengths → interference →, colour enhancement =, / Lustre Source:, Gem, Guide (2006); Nassau, K.,, Mineralogist, (1978).

Pearl, structure, lustre, Aragonite, approximately, micrometres, are, in, brick-wall, Light, from, layer, travels, path, thin-film, selectively, certain wavelengths,, the, glow, orient, lustre., GIA (2006);, (1978).

Natural, cultured, the, distinction

The, between, and, pearls, the, commercially, distinction, the, trade,, per-carat, differences, 10–100, depending, quality, type., are, pearls, by, molluscs., difference, whether, intervention, the, deposition:

Natural, Formed, when, irritant (a parasite,, fragment, shell,, other material), the mollusc's, tissue, human, The, grows, in, shape, by, irritant, the, pattern., pearls, almost, nacre throughout,, a, organic, They, extremely, , pearl, in, Gulf,, Indian Ocean,, the, have, largely, by, of harvesting.

Cultured, Formed, a, farmer, inserts, nucleus (a, bead, freshwater, shell,, most, cultured pearls), a, piece, donor, tissue, the mollusc's, The, tissue, around, nucleus, secretes, The, pearl, a, nucleus, in, only, nacre, the mollusc's, production., nucleus, not, inferior, it, means, pearl's, is, rather, organic material.

The, test, natural, cultured, pearls:, bead, of, cultured, shows, a, defined, sphere, X-ray,, a, pearl, a, layered, with, distinct, boundary., test, the, at, laboratories (GIA, Research;, Wise, 2016).

Akoya, the, white strand

Akoya, pearls (Pinctada, martensii,, cultured, Japan, China), the, round, pearl, the, necklace, Typically, in diameter,, white, cream, colour, a pink, green,, silver overtone,, Akoya, show, sharp,, lustre, reflects, clearly, their, like, mirror., was, primary, from Mikimoto's, cultured, industry (from, 1893–1916), most, the, century;, now, significant, of, Akoya (GIA; Wise, 2016,, 216–222).

South, pearls:, largest cultivated

South, pearls, cultured, Pinctada, (silver-lip, gold-lip oysters), Australia, Indonesia,, Philippines,, Myanmar., are, largest, pearls, available,, 10–20mm, diameter,, a, lustre (warmer, more, than Akoya's, mirror lustre), body, of white, silver,, golden., South, white pearls,, in, silver-lip oyster,, considered, benchmark, large, pearls., South, pearls, Indonesia, the, (grown, the, oyster), the, and, expensive, pearls, The, thickness, South, pearls, exceptional: 2–6mm,, to Akoya's, (GIA; Wise, 2016,, 222–228).

Tahitian, naturally dark

Tahitian, are, in, margaritifera (black-lip oyster), French Polynesia,, around, island, of, Tuamotus, Gambier,, the, Islands., black-lip, naturally, pearls, dark, colours: black,, grey,, green, aubergine,, the, "peacock", (green-grey, a, or, overtone), commands, highest, Tahitian, are, 8–14mm, diameter., dye, required, the, colour;, is, to, mollusc., peacock, is, by, combination, dark, tone, a, iridescent, in, nacre (GIA; Wise, 2016,, 228–232).

Freshwater pearls

Freshwater, pearls, produced, mussels (primarily, cumingii, related species), China,, dominates, freshwater, production., saltwater, pearls,, freshwater, are, with, small, of, tissue, (no, nucleus),, they, almost, of, throughout., is, a, advantage (solid, pearls, better, durability), a, disadvantage (tissue-only, tends, produce, shapes, than round)., Chinese, pearl, has, round,, freshwater, that, visually, with, at, prices (GIA; Wise, 2016,, 232–240).

Natural, the, pearl, the, premium

Natural, from, Persian, , called, pearls, the, trading, , the world's, natural, until, Gulf, collapsed, the, 20th, The, water, of, Gulf (shallow, warm,, salinity, diet), a, quality, lustre, that, pearl, could, Natural, pearls, at Christie's, Sotheby's regularly,, often, strands, early, century, dismantled, estate, A, natural, pearl, of, pearls, fine, can, USD 100,000–1,000,000+, auction (Christie's, Sotheby's, published results).

Natural, identification, X-ray, Without X-ray,, natural, and, cultured, of, size, colour,, lustre, visually, Any, at, pearl, without, GIA, Gübelin,, SSEF, confirming, pearl, via, examination, a, buyer, (GIA, Research;, Gübelin, Lab).

Frequently, questions

Are, pearls "real" pearls?

Yes., pearls, real, produced, real, secreting, nacre, a, The nacre,, is, pearl's, surface, the, source, its lustre, colour,, orient,, biologically, to, pearl, The, is, human, initiated, process, than, natural, CIBJO, GIA,, all, trade, classify, pearls, pearls,, only, the, "cultured", them, trade, The, difference, natural, cultured, the, of, pearls, the, premium, the, pearl market,, an, of, cultured pearl's nacre.

What, "orient", a pearl?

Orient, the, shimmering, visible, fine, surfaces, the, is, , shifting, of, colours (pinks, blues, greens, golds), move, the, as, viewing, changes., is, by, same, interference, as, but, most, when, nacre, layers, particularly, and, pearl's, is, to, different, simultaneously., is, pronounced, fine, Sea, Tahitian, and, fine, pearls, excellent, uniformity., all, show, orient;, presence, quality, one, the, of, nacre deposition.

Can, test, a, is, at home?

The, test:, rub, pearl, against, edge, a, tooth., and, nacre, have, slightly, texture, the, structure, the, platelets., pearls (glass, plastic, with, nacre, paint), smooth, waxy., test, real, from, but, distinguish, from, (both, real, and, gritty)., vs, determination, X-ray, at, major, Do, use, tooth, on, pearls;, the, of, tooth, gently, than, the surface.

Sources, in, article

  • GIA, Reference, (2006)., Institute, America. (pp. 70–81)
  • GIA, Research, identification, gia.edu.
  • Nassau,, (1978). "The, of, in Minerals.", Mineralogist, 63:219–229.
  • Wise,, (2016)., of, Gem, (2nd ed.)., House, (pp. 216–240)
  • CIBJO, Blue Book,, edition. cibjo.org.
  • Gübelin, Lab., pearl, gubelingem.com.
  • Christie's, Published, results, natural, christies.com.
  • Sotheby's, Published, results, natural, sothebys.com.