Ruby Zoisite is a captivating gemstone with a distinct combination of vibrant hues. This striking material blends rich green, deep red, and occasional black. Its characteristics provide insight into why this unique stone holds appeal in the world of gemstones.
What is Ruby Zoisite
Ruby Zoisite is a naturally occurring rock, not a single mineral. It is composed primarily of three distinct minerals: green zoisite, opaque ruby (corundum), and often black hornblende. The zoisite provides a green backdrop, while ruby inclusions appear as pink or red accents, creating contrast. Hornblende can appear as dark spots or streaks throughout the material.
The stone’s appearance is characterized by its mottled pattern, where the colors intermingle. Zoisite is a calcium aluminum sorosilicate mineral, and ruby is a red variety of corundum, an aluminum oxide. On the Mohs scale of hardness, zoisite ranges from 6.5 to 7, while ruby inclusions are harder at 9.
Where Ruby Zoisite is Found
Ruby Zoisite was first discovered in 1954 in northeastern Tanzania, specifically within the Longido mining district. This region remains the primary source for the gemstone, and it is considered the only major origin globally. Smaller-scale mining operations also contribute to its extraction.
The formation of Ruby Zoisite occurs under specific geological conditions involving metamorphism. This process transforms existing rocks through heat, pressure, and chemical changes, allowing for the natural fusion of zoisite and ruby. The metamorphic activity in the Tanzanian region, near Mount Kilimanjaro, facilitates the crystallization of this multi-component stone.
Is Ruby Zoisite Truly Rare
The rarity of Ruby Zoisite is nuanced. While the overall material is abundant, especially from its primary Tanzanian deposits, high-quality, gem-grade ruby crystals within the zoisite matrix are less common. The rubies found in Ruby Zoisite are opaque and not suitable for faceting into transparent gemstones, distinguishing them from transparent rubies used in fine jewelry.
Large geological deposits of the combined material exist, making it widely available. However, pieces exhibiting a desirable balance of vibrant green zoisite and well-defined, richly colored ruby inclusions are scarcer. The presence of black hornblende inclusions can also affect aesthetic appeal, with pieces featuring minimal black being more sought after. The distinction between geological abundance and the market availability of aesthetically pleasing, high-grade specimens is important when discussing its rarity.
How Rarity Impacts Value
The market value of Ruby Zoisite is influenced by factors beyond its overall availability. The quality and distribution of ruby inclusions determine its price. Specimens with a higher concentration of well-defined, vivid red or pink ruby sections are more valued than those with sparse or faint ruby presence.
The vibrancy of the green zoisite and the aesthetic appeal of the color patterns also contribute to its worth. While high-quality pure ruby can command high prices, Ruby Zoisite is more affordable, ranging from $0.50 to $3 per carat for cabochons and $10 to $100 per carat for higher-grade material. This stone is commonly cut en cabochon, polished into smooth shapes, or carved into ornamental figures, rather than being faceted like transparent gemstones. Its unique visual appeal and the limited supply of top-tier specimens contribute to its standing as a decorative stone.