Cordierite is a captivating blue to violet crystal, notable for its strong pleochroism – displaying different colors when viewed from varying angles. Often referred to as iolite, New Zealand blue quartz, or even “water sapphire” due to its unique optical properties, this semi-precious gemstone holds a fascinating place in both history and modern gemology. While not one of the traditionally recognized birthstones, cordierite serves as a budget-friendly alternative for those born under the signs of Taurus and Sagittarius. This article will delve into the history, geological origins, gemological properties, and metaphysical beliefs surrounding this intriguing stone, as well as provide guidance on its care and maintenance.
History and Lore
The mineral cordierite was officially discovered in 1813 in Níjar, Almería, Spain, and was named in honor of French geologist and mining engineer Pierre Louis Cordier, who first studied the species in 1809, initially naming it “dichroite.” However, its story extends far beyond its formal scientific recognition.
Cordierite is popularly known as the “Viking’s Compass,” a moniker stemming from an old Norse legend. Vikings purportedly utilized the pleochroic properties of cordierite gems for navigation. These gems acted as polarizing filters, enabling sailors to locate the sun’s position even on overcast days. By observing which side of the gem appeared lighter, they could determine the sun’s axis and maintain their course. While the extent to which this practice was widespread remains a subject of lore, it underscores the historical appreciation for the stone’s unique optical characteristics.
Historically, cordierite has also been known by several other names, including Steinheilite, named after Count Fabian Gotthard von Steinheil, former Governor General of Finland. Today, its primary use isn’t in navigation or even as a prominent gemstone, but rather in industrial applications like the creation of kiln shelves, prized for their thermal shock resistance and non-stick properties.
Geological Formation and Sources
Cordierite forms in metamorphic rocks, specifically in gedrite-cordierite-biotite gneiss and quartz-cordierite veins. Recent studies have focused on occurrences in British Columbia, Canada, specifically from the Blue Bear and Blue Arrow claims. These locations yield violet-blue, strongly pleochroic cordierite as subhedral to euhedral porphyroblasts within the gneiss. Crystals averaging 5 cm across have been observed, with the largest recorded specimen measuring 11.3 cm in length.
The quality of cordierite from these locations varies. While some crystals are heavily fractured and contain acicular inclusions, others exhibit zones suitable for polishing into gemstones. The largest faceted gemstones reported from these localities are a 2.0 ct stone from Blue Arrow and a 4.46 ct windowed stone from Blue Bear. Specific gravity measurements were obtained hydrostatically, and refractive indices were measured using a Kruss professional refractometer with monochromatic sodium light.
Gemological Properties
Cordierite’s chemical formula is (Mg,Fe)2Al3(AlSi5O18). It is a strongly pleochroic mineral, meaning it exhibits different colors depending on the viewing angle. This is its most defining characteristic. When cordierite grows without obstructions, it typically forms short prismatic crystals with rectangular, cluster-like cross-sections. Twinning can occur, resembling plagioclase, but can be distinguished through thin section staining.
Here’s a summary of key gemological properties:
| Property | Description |
|---|---|
| Chemical Formula | (Mg,Fe)2Al3(AlSi5O18) |
| Pleochroism | Strong, displaying different colors with angle |
| Crystal System | Orthorhombic |
| Hardness | Durable, but susceptible to cleavage |
Cordierite’s distinct cleavage in one direction makes it vulnerable to breakage, particularly when used in jewelry items prone to impact. Therefore, protective settings are recommended for rings and other such pieces.
Symbolism and Metaphysical Beliefs
Cordierite is often associated with stability, clarity, and calmness, much like other blue gemstones. It is believed to act as a guiding stone, supporting the physical, emotional, and spiritual well-being of those who work with it. It is sometimes referred to as a “compass stone” for its purported ability to direct individuals towards their goals.
Metaphysically, cordierite is thought to aid in overcoming physical ailments such as headaches, insomnia, body aches, stress, digestive issues, poor vision, mental decline, and even hair loss. Emotionally, it is believed to stabilize emotions, calm the mind, and foster creativity, problem-solving, and clear decision-making. It is said to remove hesitations and distractions, allowing for focused action.
Cordierite is considered a traditional gemstone honoring a 21st wedding anniversary and a less expensive alternative to sapphires for a 45th anniversary. It is also recognized as an alternative zodiac stone for Taurus and the traditional stone for Sagittarius.
Care and Cleaning
Cordierite, while durable enough for various uses, requires specific care to maintain its beauty and integrity. Cleaning should be performed with lukewarm water, gentle soap, and a soft-bristled brush. Prolonged exposure to water should be avoided, as it can potentially cause cracking.
It is important to protect cordierite from harsh chemicals, perfumes, cosmetics, ultrasonic cleaners, steam cleaners, abrasive minerals, and sudden temperature changes. For safekeeping, it should be stored in a soft, fabric-lined box or pouch, separate from harder gemstones to prevent scratching or damage.
Conclusion
Cordierite, with its captivating pleochroism and rich history, is a gemstone that continues to fascinate. From its legendary use as a “Viking’s Compass” to its modern applications in industrial settings and its growing popularity as an alternative birthstone, cordierite offers a unique blend of scientific intrigue and cultural significance. Its purported healing properties and symbolic associations further enhance its appeal, making it a compelling choice for gemstone enthusiasts and those seeking a stone with both beauty and meaning.