GIA

GIA

giagrams

Here’s our quick list of some of the most dazzling special optical effects, called phenomena, in the world of gems: - Asterism / Star Gem: When light hits tiny needle-like inclusions just right, gems like sapphire and ruby can show a mobile star pattern on their surface. - Cat’s Eye (Chatoyancy): A single bright band of light stretches across the gem, like the slit pupil of a cat. Most famous in chrysoberyl, it can also appear in moonstone, emerald and tourmaline. - Labradorescence: A dramatic flash of iridescent blue, green or gold seen in labradorite. Caused by layers of feldspar inside the stone scattering light. - Play-of-Color: The rainbow fire seen in precious opals. Caused by microscopic spheres inside the gem that diffract light like a prism. - Adularescence: A soft, floating sheen (often bluish) that hovers just beneath the surface of moonstone. - Iridescence (called Orient in pearls): A rainbow-like shimmer that drifts across the surface. Common in pearls, fire agate, and ammolite. - Color Change: A gems color appears different under varying light. Most famously seen in alexandrite, which can shift from red to green, but can also occur in sapphires and garnets. - Aventurescence: A glittery, metallic sparkle caused by tiny mineral inclusions. Most famously seen in aventurine quartz and sunstone. Which phenomenal gem is your favorite? Read in-depth articles about each gemstone phenomena in the Summer 2025 edition of Gems & Gemology at the link in our bio.

10.07 21:15

GIA 的更多帖子

Don’t cut corners when it comes to diamond cut! Here are some fun facts about diamond cut grades you might not know: - Cut grades are based on seven factors: brightness, fire, scintillation, weight ratio, durability, polish and symmetry. - Only round brilliant diamonds receive cut grades. All other shapes receive polish and symmetry evaluations. - Cut might just be the most important of the 4Cs! An Excellent cut makes a diamond bright and lively. A Poor cut leaves it dull and lifeless. - Thanks to GIA’s introduction of diamond cut grades, most diamonds on the market today have an Excellent or Very Good cut. Learn more about diamond cut at the link in our bio.
In September, the GIA Museum featured a special exhibit for Converge attendees! The iconic Bismarck Sapphire Necklace, containing a 98.57‑carat cushion-cut “Royal Blue” sapphire mined in Myanmar (formerly Burma), was highlighted at the Temples & Treasures of Southern Asia exhibit during GIA’s Open House. This magnificent sapphire necklace typically resides at the @SmithsonianNMNH in Washington DC but was graciously loaned to us for analysis and display for Converge. The Bismarck Sapphire Necklace went through GIA’s rigorous gemological identification and geographic origin analysis where GIA confirmed Burmese origin via trace-element analysis and microscopic examination of inclusions. Did you get a chance to view this amazing piece during Converge? Bismarck Sapphire Necklace Courtesy of the Department of Mineral Sciences, National Museum of Natural History, Gift of Countess Mona von Bismarck
Can this historic emerald reveal new discoveries about ancient trade routes? This 16th-century pendant, linked to Catherine de’ Medici, was long believed to feature Colombian emeralds. But it was recently found to contain emeralds from Pakistan’s Swat Valley! Working with historians and the Museum of the National Library of France, gemologists analyzed the stones and discovered key features unique to Swat emeralds. The gems contain high iron and chromium with low vanadium levels, plus mica and rounded multiphase inclusions. These are characteristics that definitively ruled out South American origins. This discovery offers rare evidence of early trade routes between Asia and Europe and suggests other royal jewels may also contain emeralds from Pakistan. 🇵🇰 Read more about this stunning and historic piece and see the photomicrographs that helped determine origin in a recent issue of G&G at the link in our bio. Photos courtesy of National Library of France.
Stones of this size, color and clarity are extraordinarily rare! This exquisite 9.02-carat diamond, graded Fancy Vivid Pink and Internally Flawless by GIA, is a true marvel of nature. 🩷 It is classified as type IIa—the most chemically pure diamond type. From residing under extreme pressures at high temperatures deep in the Earth, to emerging via explosive volcanic eruptions, it’s no wonder that some diamonds are stressed! These natural stresses can result in plastic deformation, creating crystal irregularities that can affect how the diamond absorbs light. Often this leads to features that impart a brown hue, but for a lucky few the resulting color is pink! Very few diamonds survive this tumultuous journey, making this dreamy gem not only breathtaking, but a geological rarity. Learn more about pink diamonds on our website at the link in our bio.
October’s birthstones, opal and tourmaline, are bursting with color and rich in legend. Opals are famous for their vivid play-of-color, so mesmerizing that the Romans believed they were the most powerful of all gems. In Bedouin lore, opals were said to contain lightning and fall from the sky during storms. ⚡ Today, top opal sources include Australia, Ethiopia, Mexico and Brazil. Tourmaline comes in every color of the rainbow—sometimes having numerous colors in one stone! Its name comes from the Sinhalese word turmali, meaning “mixed gems.” According to Egyptian legend, tourmaline traveled along a rainbow during its journey to Earth, which is why it appears in so many colors. Top tourmaline sources include Brazil, Sri Lanka, Afghanistan, Mozambique, Madagascar, Nigeria and the U.S., especially California and Maine. Whether you love opal’s shifting fire or tourmaline’s color variety, October’s birthstones are full of beauty, meaning and surprise. Learn more about October’s birthstones at the link in our bio.
Rising in a blaze of color, the 26.65-carat Phoenix Padparadscha sapphire lives up to its legendary name. Its vibrant color not only recalls the mythical phoenix but also reflects the meaning behind the name padparadscha, derived from the Sinhalese word for “lotus blossom”— a reference to the gem’s delicate, sunset-like hue. 🌅 Padparadscha sapphires are among the rarest and most prized sapphires in the world. Only stones in the pinkish-orange to orangey pink color range are classified as padparadscha by GIA. Gems over two carats are uncommon, and those over five are considered rare. The Phoenix, at an impressive 26.65 carats, combines intense even color with exceptional clarity, making it one of the finest known examples of its kind. This prized gem also hails from Sri Lanka, the most renowned source of padparadscha sapphires in the world. GIA gemologists observed that the Phoenix Padparadscha has internal characteristics highly consistent with sapphires mined in Sri Lanka. The stone displays unaltered transparent and opaque crystals, inclusion stringers, reflective particle clouds and fluid fingerprints. Solid inclusions that exhibit no visual evidence of alteration are a good indication that this sapphire had not been subjected to heat treatment. Linear color zoning consistent with natural corundum was also observed, but this zoning did not affect the face-up color appearance. Have you seen a padparadscha sapphire as exquisite as this?
Meet the XUAN Diamond! 💎 This stone is an incredible 10.60 carats and boasts a Fancy Vivid Blue color grade with Internally Flawless (IF) clarity, expertly graded by GIA. Over its 70-year history, GIA has examined nearly every natural blue diamond ever polished—and XUAN stands among the rarest. What sets XUAN apart? Of all the diamonds submitted to GIA each year, only 2% are Fancy color. Unmodified blue is amongst the rarest colors, with few diamonds featuring the saturation necessary to receive the highly coveted Fancy Vivid grade. Pair that with an Internally Flawless clarity and impressive size, and XUAN stands out as a natural marvel. As a type IIb diamond, its intense blue hue is caused by trace amounts of boron, which also gives it the rare ability to conduct electricity. Experts even believe it was likely sourced from the famed Cullinan Mine in South Africa. What do you think of this incredible gem? Learn more about Fancy color diamonds on our website at the link in our bio.
This stunning diamond has us starstruck 🤩 The stone in Taylor's ring is believed to be an old mine cut diamond. This vintage style has surged in popularity in recent years for its unique personality and charm. If you want to learn more about choosing an old mine cut diamond, visit the blog linked in our bio. Photo from Taylor Swift @taylorswift
Spinel is a durable gem that exists in nearly all the colors of the rainbow. 🌈 Once called “the great imposter” because red spinel was often mistaken for ruby, spinel is now highly popular and beloved in its own right. Save our easy guide to know how to pick the best one for you: COLOR: The most sought-after spinels feature vibrant red to purplish-red hues. Vivid blue stones with high cobalt content known as “cobalt spinel” are also incredibly valuable. Neon pink varieties are sometimes nicknamed “Jedi spinel.” More affordable options include violet and gray spinels, admired for their cool tones and steely gleam. CLARITY: Spinels are expected to be free of eye-visible inclusions. Visible inclusions can reduce desirability unless the spinel has extraordinary size and color. CUTTING STYLE: Due to spinel’s rarity, most high-quality crystals are cut in non-standard sizes to preserve weight. Standard-cut or calibrated cuts, often from gem-quality rough, are typically used for commercial-quality spinel. CARAT WEIGHT: The largest gem-quality spinel crystal in the world is around 500 carats, but most gem-quality spinels are under five carats. Price increases exponentially as carat weight increases. Learn how to pick the best spinel for you at the link in our bio.
『关注公众号 instome 解锁更多功能』

微信扫描二维码登录