Birthstone Guide — Western & Indian Traditions

The birthstone tradition has ancient roots. The twelve gems set in the Breastplate of Aaron — described in the Book of Exodus — were the original twelve-stone system, though these were associated with the twelve tribes of Israel rather than calendar months. The connection to months and zodiac signs developed gradually through the work of early theologians: Josephus (1st century CE) and St. Jerome (5th century CE) each drew parallels between the breastplate gems, the months, and the zodiac [Kunz, G.F., 1913. The Curious Lore of Precious Stones. J.B. Lippincott].

The modern practice of wearing a single gem corresponding to one's birth month became popular in 18th-century Poland and spread throughout Europe over the following century. In 1912, the American National Association of Jewelers (now Jewelers of America) standardized the first modern birthstone list — the most widely used version today. The list was updated in 2002 to add tanzanite as a December birthstone and in 2016 to add spinel as an August stone [American Gem Society, ags.org].

Every stone on the list has a story that predates the 1912 standardization by centuries or millennia. Garnet has been worn as a talisman for 5,000 years. Diamond adorned the sword hilts of medieval warriors. Pearl was found in the tombs of Egyptian pharaohs. The standardization organized an already-ancient human habit.

A gemstone is any mineral (or organic material, in the case of pearl, amber, and coral) with sufficient beauty, durability, and rarity to be used in jewelry. The Gemological Institute of America (GIA) — the world's leading authority on gemological standards — evaluates gems using four criteria: cut, clarity, color, and carat weight, known as the "4 Cs."

The chemistry behind gem color is fascinating. Rubies and sapphires are the same mineral (corundum, aluminum oxide) — the difference is trace elements. Chromium gives ruby its red; iron and titanium give sapphire its blue. Emerald and aquamarine are both beryl — chromium creates emerald's green, iron creates aquamarine's blue-green. The connection between the same mineral and such different visual experiences illustrates how dramatically trace elements can transform a stone's appearance.

Gem hardness (measured by the Mohs scale) affects how a stone should be worn and cared for. Diamond at Mohs 10 is the hardest natural substance on Earth. Topaz (Mohs 8) is hard but cleaves easily. Pearl (Mohs 2.5–4.5) is soft and requires gentle handling. Knowing the hardness of your birthstone tells you a great deal about how to treat it. [Source: GIA Gem Encyclopedia, gia.edu]

Every major human civilization has assigned meaning to gemstones. Ancient Egyptians buried their royalty with garnet necklaces and emerald amulets. The Romans ranked pearls above all other gems and passed laws restricting who could wear them. Medieval European clergy wore sapphires to represent Heaven. Mughal emperors commissioned emeralds engraved with prayers from the Quran. Hawaiian tradition holds that the green olivine crystals on certain beaches are the tears of Pele, the volcano goddess.

These meanings — accumulated across millennia of human attention and attribution — are what makes gemstones more than beautiful rocks. They carry cultural weight that has compounded through time. Whether or not a ruby literally confers courage or a pearl genuinely promotes wisdom, the accumulated human belief in those properties is itself a historical fact worth knowing.