Coral, a gemstone formed from the skeletal remains of marine invertebrates, holds a unique position in the history of adornment and belief. While not consistently listed as a primary birthstone in modern systems, historical texts reveal its significant association with certain months and astrological signs, and its enduring appeal as a material for jewelry and ornamental objects. This article will explore the historical use, geological origins, gemological properties, symbolism, and identification of coral, drawing upon historical and gemological literature.
History and Lore
The use of coral dates back millennia, with evidence of its employment as ornamentation found in prehistoric archaeological sites. Ancient civilizations recognized coral not merely for its aesthetic qualities but also for its perceived protective powers. References to coral appear in ancient texts, often linked to beliefs surrounding fertility, healing, and warding off evil.
Early writings detail the association of coral with various cultures. Muzio (1) provides a comprehensive overview of ancient understanding of gemstones, including coral, noting its significance in historical contexts. Bannerman-Phillips (1) touches upon the broader use of amulets and birthstones, placing coral within a tradition of attributing protective qualities to gemstones.
The 18th and 19th centuries saw a flourishing trade in coral, particularly Italian coral, prized for its deep red hues. Gatterer (1) details publications from this period dedicated to the recognition and valuation of gemstones, including coral, for use in jewelry and craftsmanship. The demand for coral spurred exploration and harvesting, leading to a greater understanding of its biological origins.
By the 20th century, the standardization of birthstone lists began to emerge. Heller & Son (1) published materials outlining their own naming conventions for birthstones, including variations that incorporated coral. Heaps (1) discusses the evolution of birthstone lore, noting the discrepancies between traditional beliefs and modern interpretations. The company provided their own names for corundums or spinels, but also gave the "traditional" stones.
Geological Formation and Sources
Coral is not a mineral in the traditional sense, but rather an organic gemstone. It is formed by colonies of tiny marine animals called polyps, which secrete a calcium carbonate skeleton. Over time, these skeletons accumulate to form coral reefs and branches, which are then harvested for their gemological properties.
While the provided sources do not detail specific modern mining locations, they indicate historical sources and methods of acquisition. Muzio (1) describes coral fishing and mining practices as understood in earlier centuries. Helm (1) details chemical analyses of amber, a similar organic gemstone, demonstrating early scientific interest in the origins of such materials. The Wise mine in New Hampshire is mentioned as a source of pale green material suitable for faceting (1), though this is not coral.
Gemological Properties
The gemological properties of coral contribute to its unique appeal. Coral is relatively soft, with a Mohs hardness of 2.5 to 4, making it susceptible to scratching and abrasion. Its chemical composition is primarily calcium carbonate (CaCO3), with trace elements contributing to its color variations.
The most prized color in coral is a deep, vibrant red, often referred to as “oxblood” coral. However, coral also occurs in shades of pink, orange, white, and black. The color is influenced by the depth and environment in which the coral grows, as well as the presence of pigments within the polyps.
Bannister (1) discusses the relationship between density and refractive index in silicate glasses, a technique used to identify imitation gemstones. While not directly addressing coral, this highlights the importance of gemological testing in distinguishing natural coral from synthetic or imitation materials. Brown & Gordon (1) provide a comprehensive overview of gemological properties, though their focus is primarily on planetary gems as described in ancient Sanskrit texts.
A table summarizing key gemological properties, based on general gemological knowledge (as the sources do not provide a comprehensive list), is as follows:
| Property | Value |
|---|---|
| Chemical Formula | CaCO3 |
| Hardness (Mohs) | 2.5 - 4 |
| Specific Gravity | 2.6 - 2.7 |
| Refractive Index | 1.43 - 1.66 |
| Luster | Vitreous |
| Transparency | Translucent |
Symbolism and Metaphysical Beliefs
Throughout history, coral has been imbued with symbolic meaning. Ancient cultures associated it with protection against evil spirits, fertility, and healing. Bannerman-Phillips (1) explores the broader context of amulets and birthstones, suggesting that coral, like other gemstones, was believed to possess talismanic powers.
The Sanskrit texts translated by Brown & Gordon (1) detail the astrological characteristics and effects of gemstones, though coral is not specifically highlighted within the provided excerpt. However, the general framework suggests that gemstones were believed to influence various aspects of life by appeasing planets and removing obstructions.
Care and Cleaning
Due to its relative softness, coral requires careful handling and cleaning. It is susceptible to scratches from harder materials and can be damaged by harsh chemicals. Cleaning should be done with a soft cloth and mild soapy water. Avoid ultrasonic cleaners and steam cleaners, as these can damage the coral’s structure. Polishing should be done with extreme care to avoid removing the surface layer.
Conclusion
Coral, a gemstone born of the sea, has captivated humanity for millennia. From its ancient origins as a protective amulet to its modern role as a beautiful adornment, coral’s enduring appeal lies in its unique combination of natural beauty, historical significance, and symbolic meaning. While its status as a definitive birthstone may vary, its place in the lore of gemstones remains secure, a testament to its enduring fascination.