The concept of birthstones—gemstones assigned to specific months of the year—is a deeply ingrained tradition in modern culture. For many, the choice of a gemstone for an engagement ring, a pendant, or a birthday gift is guided by this long-standing list. Yet, the journey from ancient religious artifacts to the standardized, commercially-driven list we know today is a complex narrative of religious doctrine, cultural evolution, and industrial standardization. The assignment of specific gems to specific months was not the work of a single authority but a gradual process shaped by historical texts, astronomical beliefs, and, ultimately, modern trade organizations seeking to create a stable and marketable tradition.
The origins of this practice are rooted in antiquity. The earliest and most profound influence comes from the Hebrew Bible, specifically the Book of Exodus, which describes the breastplate of the high priest Aaron. This sacred garment was set with twelve distinct gemstones, arranged in four rows of three, representing the twelve tribes of Israel. The text in Exodus 28:15–30 provides the foundational list of gems, though the exact identification of these ancient stones has been a subject of scholarly debate for centuries. This religious artifact established the powerful association between a select group of twelve stones and a system of twelve symbolic entities.
The pivotal transition from this religious context to a personal, birth-related talisman began with the writings of first-century historian Flavius Josephus. In his Antiquities of the Jews, Josephus was the first to draw a connection between the twelve stones of Aaron's breastplate and the twelve signs of the zodiac. This linkage was further developed by St. Jerome in the 5th century AD. These early scholars proposed that each of the twelve stones possessed special powers corresponding to its associated astrological sign. This concept gave rise to the practice of owning all twelve gems and wearing the one appropriate for the current zodiac period, a tradition that would persist for many centuries.
The Evolution from Zodiacal Talismans to Monthly Birthstones
For several centuries following the interpretations of Josephus and St. Jerome, the prevailing practice was not to wear a single gemstone for one's entire birth year. Instead, individuals would possess a collection of twelve stones, wearing a different one each month to align with the corresponding zodiacal sign and harness its purported therapeutic or talismanic benefits. This approach was more dynamic, reflecting the changing celestial influences throughout the year rather than a fixed association with one's birth.
The significant shift toward the modern custom of wearing a single gemstone for one's entire life is a more recent development. According to the work of the influential gemologist George Frederick Kunz, this practice can be traced to 18th-century Poland. It was here that the tradition of wearing a specific gemstone corresponding to one's birth month, rather than the current zodiacal sign, became popularized. This marked a crucial turning point, moving the focus from a cyclical, astrological system to a fixed, personal identifier tied to the calendar month of one's birth.
Throughout the 16th to 19th centuries, the list of stones associated with each month was far from uniform. It varied significantly across different regions and cultures, often influenced by the availability of certain gems and local folklore. This lack of a definitive list created a fluid and often confusing tradition. It was this very inconsistency that set the stage for a major development in the late 19th and early 20th centuries, driven by the burgeoning American jewelry industry.
The Commercial Catalyst: George Frederick Kunz and Tiffany & Co.
The modern birthstone list owes a great deal to the efforts of George Frederick Kunz, a self-taught gem expert and America's first great gemologist. Kunz was instrumental in reviving and standardizing the birthstone tradition for a modern audience. In 1891, while employed by the prestigious New York jeweler Tiffany & Co., Kunz published a 36-page booklet titled Natal Stones: Sentiments and Superstitions Connected with Precious Stones.
This publication was more than a simple historical overview; it was a consolidation of centuries of informal tradition. Kunz documented the various historical associations and presented them in a way that was accessible and appealing to the general public. The booklet proved to be a remarkable success, not only for its informational content but also for its commercial impact. Jewelers across the nation observed a significant boost in the sales of natal-related gemstones and jewelry, demonstrating a strong public appetite for a standardized tradition. Kunz's work effectively laid the commercial groundwork for the formal standardization that would follow.
The Standardization of Birthstones
The turn of the 20th century marked the final step in creating the birthstone list we recognize today. In 1906, the newly founded American National Retail Jewelers Association (which would later become Jewelers of America) took the first official step by replacing the archaic term "natal stone" with the more contemporary and marketable term "birthstone."
The pivotal moment arrived in 1912. The National Association of Jewelers (a predecessor organization to the Jewelers of America) convened and established a definitive, standardized birthstone list for the United States. This was a radical departure from the historical and often opaque gems of the ancient lists. The association made a clear commercial decision to modernize the list by replacing four of the original stones with the "big four" precious gemstones: diamond, ruby, emerald, and sapphire. These faceted, transparent gems were highly prized in the modern jewelry market. Furthermore, popular gems of the time, pearl and opal, were also added, replacing two other traditional stones. The list was further refined by reassigning stones based on color associations; for instance, the "warm" colored ruby was moved to July, while the "cool" colored turquoise was shifted to December.
This 1912 standardization was not without its critics. George Frederick Kunz himself, in his 1913 classic The Curious Lore of Precious Stones, voiced his objection to the sudden inclusion of faceted precious gems and the rearrangement of stones like ruby and turquoise. His concerns highlight the tension between historical tradition and the commercial imperatives of the modern jewelry trade.
The American list has not remained entirely static since 1912. It has been modified several times to reflect changing tastes and market availability. In 1952, the Jewelry Industry Council of America expanded the list, adding alexandrite for June, citrine for November, pink tourmaline for October, and zircon for December. More recently, tanzanite was added as an alternative birthstone for December in 2002, and spinel was added to August in 2016.
It is crucial to note that the American list is not the only "official" list. Other countries have their own standards. For example, in the 1930s, Britain’s National Association of Goldsmiths created its own birthstone list, which is still in use in Great Britain today. This variation underscores that the assignment of birthstones is ultimately a cultural and commercial construct rather than a universal scientific or historical mandate. The modern practice of choosing a birthstone is typically a choice between the "modern" list established in 1912 and subsequent additions, and the "traditional" list, which includes the gems historically associated with each month.
Conclusion
The decision of who "decides" the birthstones is not attributable to a single individual or a single point in time. The tradition is a layered tapestry woven from ancient religious texts, first-century historical interpretations, medieval zodiacal practices, and finally, the commercial standardization efforts of 20th-century American jewelers. The journey from Aaron's breastplate to a Tiffany & Co. marketing booklet and finally to an official list by a national trade association illustrates how a cultural tradition can be shaped, refined, and popularized for a new era. Today's birthstone list is a product of this rich history—a blend of ancient lore and modern commerce.