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By Reviewed By Andreas Zabczyk Jan 22, 2014 Updated Jan 17, 2019

Hackmanite Gemstone Information

Hackmanite Gemstones from GemSelect - Large Image

About Hackmanite - History and Introduction

Hackmanite is an exceptionally rare sulfur-rich variety of sodalite which exhibits tenebrescence (the ability of minerals to change color when exposed to sunlight). It was first discovered in Greenland in 1896 by L. C. Boergstroem, and was later named after Victor Axel Hackman (1866-1941), a Finnish geologist. However, it wasn't until recently (1991) that the first gem-quality hackmanite deposit was discovered in Quebec, Canada.

Hackmanite appears pale to deep violet when first mined, but once exposed to sunlight, the color quickly fades to grayish or greenish-white. When placed back into a dark place or when exposed to short wave ultraviolet light, the violet color slowly returns. The change in color can be seen within seconds of being exposed to sunlight, but the return of the original color can sometimes take up to a week. The tenebrescence effect can be repeated indefinitely, but is detroyed by heating.

The tenebrescence effect seen in hackmanite is the rarest of all gemstone optical phenomena. It is often confused with the 'color change' phenomenon, where materials can shift color under different types of light sources. Another term for tenebrescence is 'reversible photochromism'. A common example of reversible photochromism can be seen in everyday color-change eyeglass lenses. Color-change eyeglasses darken when exposed to sunlight and lighten up again when they are brought indoors. The effect is caused by a photochemical reaction to UV radiation and is known to occur in only a few rare materials.

Hackmanite Gemstones

Identifying Hackmanite

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Hackmanite is member of the feldspathoid group of minerals. The feldspathoids are a group of tectosilicates which closely resemble feldspars but exhibit a slightly different structure and lower silica composition. Hackmanite is sulfur-rich chloric sodium aluminum silicate with a hardness of 5.50 to 6.00 on the Mohs scale. It has a low density or specific gravity of 2.14 to 2.40, making it one of the least dense of all gemstones (slightly denser than opal). Most hackmanite is opaque, but high quality specimens can occur transparent to translucent in form. Hackmanite can be easily identified and distinguished from its parent stone 'sodalite' by the presence of sulfur and color change tenebrescence.

Hackmanite Origin and Sources

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Hackmanite was first discovered in Greenland, but it can also be found in a few other locations, including Afghanistan, Myanmar (Burma) and Quebec, Canada.

Striking purple hackmanite originating from the lazurite mines of Sar-e Sang, Koksha Valley of Badakshan Province in Afghanistan are considered the most desirable of hackmanite stones, which are highly sought after by gem and mineral collectors.

Buying Hackmanite

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Hackmanite Color

Hackmanite appears pale to deep violet when first mined, but quickly fades to grayish or greenish white once exposed to sunlight. However, hackmanite from Afghanistan and Myanmar does the opposite and tends to change color from colorless or creamy white to pink-red or violet under sunlight. The most desirable specimens are those that change from colorless or a very light color to an intense deep purple.

Hackmanite Clarity and Luster

Most hackmanite is opaque, but fine quality crystals can occur transparent to translucent. Inclusions are common, typically as white streaks or veins composed of calcite. Hackmanite exhibits a vitreous luster when cut and polished; on fractures, luster can appear greasy.

Hackmanite Cut and Shape

Hackmanite is often faceted for collectors or display only. In most cases, hackmanite is cut and sold in slices or slabs. The most common faceted shapes include ovals and other shapes which maximize the rough carat weight. Opaque materials may be shaped into cabochons.

Hackmanite Treatment

Hackmanite is not treated or enhanced in any way. Heating of hackmanite can result in the permanent loss of tenebrescent ability.

Hackmanite Gemological Properties:

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Chemical Formula: Na8Al6Si6O24Cl2 - Chloric sodium aluminum silicate
Crystal Structure: Cubic - rhombic dodecahedron
Color: Colorless, pink, violet, gray, greenish
Hardness: 5.5 to 6 on the Mohs scale
Refractive Index: 1.48
Density: 2.14 to 2.40
Cleavage: Indistinct
Transparency: Transparent to opaque
Double Refraction None
Luster: Vitreous to greasy
Fluorescence: Strong

Please refer to our Gemstone Glossary for details of gemology-related terms.

Hackmanite: Related or Similar Gemstones:

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Sodalite Gemstones

Hackmanite is a sulfur-rich variety of sodalite. Sodalite is mostly known for its blue color, but it can actually occur colorless, gray, yellow, green, violet, blue to deep blue and pink. There are no other gemstone varieties closely-related to hackmanite and sodalite, although they both share mineralogical similarities with many of the feldspar varieties.

Other gemstones that can be easily confused with sodalite and hackmanite include many popular gemstones, such as blue lapis lazuli, blue azurite, blue lazulite and blue dumortierite quartz.

Hackmanite - Metaphysical and Crystal Healing

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Hackmanite is known as the 'stone of eternal belonging'. It is a stone which is said to remind us of how everything has its own time and place. Hackmanite encourages its wearer to recognize that all things have belonging. Hackmanite is thought to be helpful for those who suffer from harassment, fear and apprehension. It is believed to stimulate audacity and strengthen self-esteem, while encouraging feelings of happiness, confidence and contentment.

Hackmanite is sometimes referred to as the chameleon stone, and depending on the actual color state of the stone, it is thought to provide different metaphysical abilities and healing powers. Although it is not an official birthstone for any month, hackmanite is associated with the astrological sign of Sagittarius. It is believed to be an excellent stone for the throat, third eye and heart chakra.

Disclaimer: Metaphysical and Alternative Crystal Healing Powers and Properties are not to be taken as confirmed advice. Traditional, Ceremonial and Mythological Gemstone Lore is collected from various resources and is not the sole opinion of SETT Co., Ltd. This information is not to replace the advice of your doctor. Should you have any medical conditions, please see a licensed medical practitioner. GemSelect does not guarantee any claims or statements of healing or astrological birthstone powers and cannot be held liable under any circumstances.

Hackmanite Jewelry Ideas

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Hackmanite is exceptionally rare. It is considered a collector's stone and is not recommended for jewelry wear. It is relatively soft, but with its indistinct cleavage, it's actually quite durable. For those seeking incredibly rare jewelry, hackmanite could be worn with care as a pendant or brooch. On the other hand, sodalite, the more common blue sister stone of hackmanite, is quite often used for cabochon and beaded jewelry. It is also very popular for use in the making of arts and crafts as well as ornamental gemstone carvings.

Note: Buy colored gemstones by size and not by carat weight. Colored stones vary in size-to-weight ratio. Some stones are larger and others are smaller than diamond by weight in comparison.

Hackmanite: Care and Cleaning

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How to clean your gemstonesHackmanite is fairly soft compared to most other gemstones, so it may require some special care. You can clean hackmanite stones using warm water and a mild soap or detergent if needed. Be sure to rinse well to remove any soapy reside. Do not use any harsh chemicals or cleaners and avoid extreme heat. Heating hackmanite can result in the permanent loss of its desirable tenebrescent effect.

Always remove any hackmanite jewelry when participating in any strenuous physical activity, such as playing sports, doing household chores or exercising. When storing hackmanite, always store it separately and away from other gems and jewelry. If possible, it is best to wrap it in a soft cloth or place it inside a fabric-lined jewelry box.

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