THE MINERAL KORNERUPINE

• Chemistry: Mg4(Al, Fe)6(Si, Al, B)5O21(OH), Magnesium Aluminum Iron Boro-silicate Hydroxide.
• Class: Silicates
• Subclass: Nesosilicates
• Uses: As a gemstone and as mineral collection specimens.
• Specimens

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Kornerupine is a rare gemstone and an equally rare mineral specimen. Its claim to fame is its wonderful emerald green color. This color can be very close to that of emerald's; it has a similar but higher index of refraction and it even comes with the characteristic inclusions that is a hallmark of emerald. To distinguish kornerupine from emerald look for the pleochroic colors of kornerupine. Pleochroic means that different colors can be seen from different viewing angles. For kornerupine, the colors change from a yellowish-green to a brownish-red as the crystal or gemstone is turned with respect to the viewer. Green is not the only color of kornerupine as it comes in attractive browns, yellows and pinks.

Kornerupine will never replace emerald and is not really a threat as a counterfeit due to its rarity. Not only is kornerupine itself rare, but the green color is also one of its rarer colors. Kornerupine is not really cut for general public purposes but is more of a collectors stone.

Kornerupine is often found in certain gem gravels such as the ones found in Sri Lanka. These deposits, called placers, form behind the rocks and bends of rivers and are enriched in heavy grains as lighter material is carried further down stream. Kornerupine has just enough density with a specific gravity of 3.3 to be deposited with other relatively dense minerals. Many of these minerals are gemstones as well, such as sphene, iolite, sapphire, chrysoberyl, ruby, topaz, garnets, andalusite, diopside, zircon, spinel and others. Kornerupine originates as a regional metamorphic mineral before being eroded downstream.

PHYSICAL CHARACTERISTICS:

• Color is green, colorless, white, pink, yellow or brown.
• Luster is vitreous.
• Transparency: Crystals are transparent to translucent.
• Crystal System is orthorhombic; 2/m 2/m 2/m
• Crystal Habit is typically elongated prisms and as rounded grains in gem gravels.
• Hardness is 6 - 7
• Specific Gravity is 3.3+ (slightly heavier than average)
• Streak is white.
• Other Characteristics: Pleochroic yellowish-green to brownish-red and index of refraction is 1.66 and 1.69.
• Associated Minerals include quartz, orthoclase, sapphire, chrysoberyl, ruby, topaz, zircon, spinel and other gemstones found in placer deposits.
• Notable Occurrences is Ratnapura, Sri Lanka; Betroka, Madagascar; Harts Range, Australia; Kenya and the Nuuk area of Greenland.
• Best Field Indicators are color, locality, pleochroism and hardness.