Magnesiotaaffeite-2N'2S

Chemical formula: Mg₃BeAl₈O₁₆

Magnesiotaaffeite-2N'2S is an extremely rare mineral from the taaffeite group, an oxide of magnesium, beryllium, and aluminum, valued exclusively by collectors.

## Characteristics Magnesiotaaffeite-2N'2S, formerly known as musgravite, is a member of the taaffeite supergroup. It most commonly forms small, tabular or short-prismatic crystals, often with a hexagonal outline. It is typically found as single, well-formed crystals, and less frequently as granular aggregates. Gem-quality specimens are extremely rare and highly sought after. ## Physical Properties This mineral is characterized by high hardness, ranging from 8 to 8.5 on the Mohs scale, making it one of the harder oxides. It has a vitreous luster and is transparent to translucent. Its density ranges from 3.63 to 3.68 g/cm³. ## Colors and Varieties It most often occurs in shades of gray, green, and violet. Colorless, grayish-green, dark green, and grayish-violet to violet crystals are found. Some specimens may exhibit subtle pleochroism. The name "musgravite" is still used in the gemstone trade to refer to its gemological variety, although formally it is magnesiotaaffeite-2N'2S. ## History and Name The mineral was originally described in 1967 based on material from the Musgrave Ranges in South Australia and named "musgravite." In 2002, the International Mineralogical Association (IMA) reclassified it and changed its name to magnesiotaaffeite-2N'2S to reflect its chemical composition (dominant magnesium) and structural relationship with taaffeite. The name taaffeite comes from its discoverer, Richard Taaffe. ## Uses Due to its extreme rarity, magnesiotaaffeite-2N'2S has no industrial applications. Its only significance is scientific and collectible. The purest and most beautifully colored crystals are occasionally cut as very rare and valuable gemstones.

Properties

Mohs hardness: 8-8.5
Luster: Vitreous
Streak: White
Density: 3.63-3.68
Cleavage: Imperfect on {0001}
Fracture: Conchoidal to uneven
Transparency: Transparent to translucent
Crystal system: Trigonal

Diagnostic features

## Identification Identifying magnesiotaaffeite-2N'2S is very difficult without advanced analysis. Key features include very high hardness (8-8.5), vitreous luster, characteristic colors (grayish-green, violet), and hexagonal crystal outline. In the field, it is practically impossible to distinguish from taaffeite. ## Distinguishing from Similar Minerals It can be confused mainly with taaffeite, from which it requires chemical analysis (magnesium to iron and zinc ratio) or detailed crystallographic studies to distinguish. It may also resemble some spinels, beryls, or sapphires, from which it differs in optical properties and higher hardness than most of them (with the exception of sapphire). ## Crystal Forms Crystals are typically tabular or short-prismatic, often with a hexagonal cross-section. They occur as single, well-formed crystals, less frequently as granular aggregates.

Geological environment

## Genesis It is a metamorphic and metasomatic mineral. It forms in aluminum-rich rocks subjected to high temperatures, such as skarns, granulite gneisses, or marbles. It forms in a silica-poor environment. ## Mineral Associations It co-occurs with minerals such as sapphire, spinel, phlogopite, anorthite, calcite, nolanite, and periclase. ## Localities The most important localities from which specimens originate are the Musgrave Ranges in South Australia (type locality), Tunduru in Tanzania, Mogok in Myanmar (Burma), and smaller occurrences in Madagascar, Greenland, and Antarctica.

Rarity

Extremely rare

For collectors

## Quality Criteria The most highly valued are fully transparent, gem-quality crystals that exhibit intense and attractive coloration, especially in shades of violet and deep green. Large, well-formed crystals with sharp edges and no damage are extremely sought after. Clarity (lack of inclusions and fractures) significantly increases the value of the specimen. ## Market Prices Uncut crystals, even small ones, fetch prices from several hundred to several thousand dollars depending on quality. Faceted stones are among the most expensive in the world, with prices per carat potentially reaching tens of thousands of dollars, rivaling the prices of red diamonds or painite. ## Popular Localities Gem-quality specimens primarily come from Tanzania (Tunduru) and Myanmar (Mogok). Material from the original Australian locality is typically opaque and of lesser collectible value, though historically significant.

Care and storage

## Cleaning Cleaning with lukewarm soapy water and a soft brush is recommended. Ultrasonic cleaners can be used, but with caution, especially for specimens with inclusions or internal fractures. ## What to Avoid The mineral is resistant to most chemicals, but contact with hydrofluoric acid should be avoided. Despite its high hardness, it is brittle and susceptible to mechanical impact. Avoid sudden temperature changes. ## Storage Specimens should be stored in separate boxes or display cases to prevent scratching by harder minerals (like diamond) or damage to softer minerals. Due to its high value, storage in a secure place is recommended.

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