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Tanzanite: The Birthstone Of December

Bestowed as the “Stone of Magic”, Tanzanite exhibits a midnight blue to velvety violet hue. Famously unveiled to the jewellery hemisphere, by renowned jewellery emporium Tiffany & Co and renamed after the gemstones exclusive locality. The enchanting combination of high clarity, intense colour and geographical rarity, has catalysed this gem to become one of the most desired materials for adornment.

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The Stone of Magic

What is Tanzanite?

Tanzanite, is the blue to violet variety of the zoisite family, which has a composition of calcium aluminium silicate with hydroxyl. The gemstone exhibits strong pleochroism, a phenomenon which is revealed through a polarising filter and requires the gemstone to be rotated, to observe the stone from different angles. Tanzanite is a doubly refractive material, therefore when a ray of light passes through the stone, it would split into two. These rays of light, absorb different parts of the visible light spectrum (white light), resulting in different colours being seen. Tanzanite without the application of heat treatment, shows three colours (known as, trichroism): Blue, Pink and Yellow. Depending on the saturation and intensity of colour, the gemstone ranges from transparent to translucent and reflects a vitreous lustre.

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Crystal Habit

The gemstone crystallises with a prismatic crystal habit, which is classified under the orthorhombic crystal system. The well-formed crystal exhibits side pinacoid faces and a rectangular cross-section. The crystal is terminated with orthorhombic prism faces. The surface of the crystal, displays horizontal lines across the prism face, otherwise referred to as striations. The formation of the crystal often develops with jagged, broken edges or fractures at one end.

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Locality of Tanzanite

Tanzanite is named and derived from the locality of Tanzania (the Merelani Hills near Mount Kilimanjaro), where the gemstone is exclusively sourced. Tanzanite radiates an intense saturation of blue to violet, which along with its geographical rarity and high clarity, fuels the demand and attention this gemstone so deservedly receives. Although, a fairly recent find in 1967, this gemstone has vastly impacted the gemmological and jewellery world.

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Under The Loupe: Inclusions

Tanzanite rarely exhibits inclusions and possesses a high clarity, although if present, occur as: graphite, hematite or ilmenite crystals.

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Treatment

Tanzanite can be heat treated, to improve the gemstones blue to violet colour. Heating is a traditional and permeant treatment, used on a multitude of gemstones to change their colour. As a result of heating, the gemstone’s ability to display pleochroism through a polarising filter, is limited to only show two colours (known as, dichroism): blue and violet.

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Grading & Simulants

There is no standard international colour grading system for Tanzanite, or for any other coloured gemstones (except coloured diamonds). However, you may have encountered some Tanzanites in the trade, to be given an A grade, for example; AA, AAA, AAAA. This system is considered to be more of a descriptive tool, used to indicate the gemstones intensity of colour. The more A’s applied, the more saturated the body colour. It is important to acknowledge, that the "A grading system" is not a universally agreed-upon standard, used by all gemmologists. Therefore, you may not see it being used on most Gemmological laboratory reports. This grading system is more dependent on each companies opinion, rather than a general consensus that is internationally applied to all tanzanites, by all gemmologists.

Tanzanite can often be mistaken for sapphire, spinel, iolite, artificial glass, synthetic colour change corundum and synthetic blue forsterite. These can all be identified through the use of gemological testing and observations.

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The Lore of Tanzanite

Tanzanite is the material used to celebrate the 24th wedding anniversary, as well as being the birthstone of December, it is also the zodiac birthstone of Sagittarius.

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Care

Tanzanite, Zoisite: 💎 Hardness: 6.5, Brittle | 💪 Toughness: Fair to Poor | ⚖️ Stability: Good

♥️ Extreme Caution, ⚠️ Avoid: 🔨 Pressure / Knocks, 🔥❄️ Thermal Shock / Extreme Temperature Change, 🔊 Ultrasonic, 🌪 Steam Cleaners.

🔬 Gemmological Observation: Tanzanite has a low durability, which means that extra care has to be taken when worn. Avoid wearing Tanzanite-set jewellery during activities or any rough handling, such as: gardening, housework or any activity which damage could occur. If set into a ring, it would be better suited for a dress ring, rather than a ring that is worn everyday - such as an engagement ring. As this stone has a low hardness it is more susceptible to scratches and abrasions with other harder materials. It is also very brittle, which means that cleaning equipment such as ultrasonics or steam cleaners have to be avoided, as these will cause the stone to fracture.