Ruby

Ruby's defining combination is a rich red color in an extremely hard, dense stone. As corundum it sits at 9 on the Mohs scale, so it scratches quartz, topaz and glass effortlessly and is scratched by nothing but diamond, and it feels notably heavy for its size. In crystal form it grows as flat, tabular or barrel-shaped hexagonal crystals, sometimes with a distinctive six-sided outline and triangular growth marks on the faces.

Two optical clues help confirm it. Ruby is pleochroic, showing a slightly different red — more purplish versus more orangey — as the stone is tilted, which glass and garnet do not do. Many natural rubies also fluoresce a strong red under the ultraviolet present in daylight, adding an inner glow that is part of why the finest stones look lit from within; and fine silk-like inclusions are common and, when oriented, produce a six-rayed star in cabochons. A hard, dense, pleochroic red stone that glows in sunlight and carries natural silk is almost certainly ruby.

Color is the overwhelming driver of a ruby's identity and worth. The ideal is a pure, vivid, slightly blue-leaning red the trade calls 'pigeon's blood' — saturated but not so dark it goes garnet-brown, and bright with that chromium fluorescence. Stones drift toward pinkish, orangey or purplish reds, and the paler ones eventually cross the contested line into 'pink sapphire' territory, with a steep drop in price.

Origin colors the vocabulary: Myanmar's Mogok valley set the 'Burmese ruby' and 'pigeon's blood' standards over eight centuries, while the 2009 discoveries at Montepuez made Mozambique the dominant modern source by volume, with Thailand, Vietnam and East Africa also supplying the market. Some silk inclusions are tolerated and even valued when they soften and spread the color; heavy, obvious inclusions or a brownish, lifeless tone lower a stone sharply.

Ruby's pedigree is royal across cultures. Sanskrit texts called it ratnaraj — literally 'king of gems' — and imagined an inextinguishable inner fire burning within it; Burmese warriors carried rubies as talismans of invincibility, some believing the stone had to be embedded under the skin to work. European crowns hoarded 'rubies' for centuries, several of the most famous of which (the Black Prince's Ruby among them) turned out to be spinel once 18th-century chemistry could tell the minerals apart.

As July's birthstone, ruby carries associations of passion, vitality, courage and love. These meanings are cultural and symbolic rather than medical, and ruby is a stone to treasure for its beauty and history, not as a remedy. Its glowing red — the color of blood and fire — is why so many traditions independently made it the gem of life force and power.

Fine ruby is among the most valuable of all colored gemstones, and the value ladder is steep. Color sits at the top — vivid 'pigeon's blood' red with strong fluorescence — followed by size, because large clean rubies are genuinely rare and price rises sharply with carat weight. Untreated stones with a credible laboratory report command enormous premiums over the heated norm, and documented Burmese origin adds further.

Treatment status is therefore central to value rather than incidental. The overwhelming majority of rubies are heated (a stable, accepted practice), so heated stones are the affordable reality of the market and priced accordingly. The value destroyers to recognize are lead-glass-filled composites and heavily fracture-filled material, which look like clean ruby but are fragile and worth a fraction — any large, flawless, cheap 'ruby' is one of these until proven otherwise.

The trickiest impostor is composite or 'glass-filled' ruby: low-grade, heavily fractured corundum whose cracks are infused with lead glass to fake clarity and color. It is genuinely part-corundum but sold far too cheap for what it appears to be, and it is fragile — jeweler's torches, ultrasonic cleaners and even lemon juice or oven heat can etch or shatter the filling. Under a loupe it betrays trapped gas bubbles and blue-orange flashes along the healed fractures.

Lab-created ruby is the other major category: chemically real corundum grown since 1902, honest when disclosed and a fraud when not, so old family 'rubies' are not automatically natural. Softer red look-alikes — garnet, red spinel, red glass — are easier to rule out by hardness and pleochroism: ruby scratches them all, and garnet and glass show no pleochroism. For any serious purchase, a report from a reputable lab confirming natural origin and stating the treatment is standard practice and well worth the cost.

An untreated or simply heat-treated ruby is superbly durable — Mohs 9, tough, and free of easy cleavage — so it withstands daily wear as well as any colored gem and cleans safely in warm soapy water, and usually in ultrasonic and steam cleaners too. This ruggedness is part of why ruby has always been a favored stone for rings meant to be worn hard.

The vital exception is treated material. Lead-glass-filled and fracture-filled rubies must be treated as delicate: keep them away from heat, acids, ultrasonic and steam cleaning, and clean only gently by hand with a soft damp cloth, because the filling is far softer and more vulnerable than the corundum around it. When a stone's treatment is unknown, err on the side of gentle care, and store ruby apart from softer gems it can easily scratch.