Moonstone is known for its unique optical phenomenon. This effect, known as adularescence, appears as a milky or bluish interior light that appears to shimmer and glide across the stone’s surface. It arises from light scattering within the gemstone, caused by alternating microscopic layers of orthoclase and albite feldspar minerals. Ancient Romans revered moonstone, associating it with their lunar deities. Moonstone experienced a resurgence in popularity during the Art Nouveau period, becoming a favored material for jewelry designers.
Global Occurrences of Moonstone
Moonstone deposits are found across various continents. Sri Lanka stands as a traditional and prominent source, particularly renowned for producing high-quality moonstones with a desirable blue sheen and transparency. The village of Meetiyagoda in southern Sri Lanka is a significant mining area. Other notable localities in Sri Lanka include Matale, Balangoda, and Kundasale.
India is another major source, producing moonstones that exhibit a wider range of colors, including brown, green, and orange hues. The Indian subcontinent is especially known for its rainbow moonstones. Key mining regions in India include Rajasthan and Bihar.
Myanmar, historically known as Burma, has also been a source of moonstones, particularly those prized for their velvety blue adularescence and exceptional clarity. The Mogok region in Myanmar has yielded valuable, transparent moonstones.
Madagascar has emerged as a significant source, offering moonstones that can feature larger crystal sizes and a unique interplay of colors, often appearing milky-white, peach, or orange. Recent discoveries in Madagascar have included highly transparent material, including rainbow moonstone, which may display a distinct orange flash alongside blue adularescence.
In Africa, Tanzania contributes to the global moonstone supply with stones that often exhibit an attractive schiller effect. Fine Tanzanian material can be translucent to sub-transparent and display a brilliant blue sheen. Deposits have been identified in various areas. Furthermore, moonstone is found in the United States, with deposits occurring in states like New Mexico, Virginia, and North Carolina. These American moonstones typically present a more subtle sheen compared to their Asian counterparts.
Distinguishing Moonstone by Origin
Moonstones from different geographical sources often possess unique characteristics that allow for their distinction. Sri Lankan moonstones are primarily recognized for their remarkable transparency and an intense, cool blue adularescence. These gems typically have a creamy texture and are often found with minimal internal flaws.
In contrast, Indian moonstones tend to be more opaque and come in a broader spectrum of body colors, such as beige-brown, green, or orange. Many Indian moonstones are categorized as “rainbow moonstones,” exhibiting multiple colors due to specific mineral inclusions. They can display both blue and rainbow light, and often contain internal features referred to as “ice cotton cracks.”
Myanmar moonstones are notable for their velvety blue adularescence and exceptional clarity, historically being among the most valuable for their strong blue sheen. These stones often exhibit a vitreous body, typically with a weaker blue light and few internal imperfections.
Madagascar moonstones can vary, showing milky-white, peach, or orange adularescence. Some newer finds from Madagascar are highly transparent and may exhibit a distinct orange flash in addition to blue adularescence. It is important to note that some “Madagascar moonstone” is, in fact, a variety of labradorite, displaying labradorescence (a vibrant, rainbow-like shimmer) rather than the classic adularescence. Moonstones from the United States generally feature a more subtle sheen compared to their Asian counterparts.