search
  • Sign In
    Sign Up
  • English speaking customer support only

    Toll Free - USA & Canada only:
    1-800-464-1640

    International:
    +66-39303404

  • Change Language
  • USD

Hackmanite Tenebrescence


Buy hackmanite
Hackmanite from Afghanistan

One of the most unusual optical phenomena in the mineral world is something known as tenebrescence. It refers to the ability of a mineral to change color when exposed to sunlight, and for the process to be reversed when the light changes. Another term for this phenomenon is reversible photochromism.

Tenebrescence is different from the color change phenomenon, where a gemstone displays a different color when viewed under different lighting. A color-change sapphire, for example, does not undergo a persistent color change when viewed under natural light. As soon as the lighting changes to incandescent, the apparent color of the sapphire changes immediately as well. This is because color-change gems have multiple transmission windows. A gemstone that absorbs all frequencies except for blue and red light will appear blue when the light is rich in blue wavelengths (e.g., sunlight) and red when the light is rich in red wavelengths (e.g., incandescent lighting).

Reversible photochromism is the effect displayed by, for example, color-change eyeglass lenses, that darken in sunlight, and then lighten again when the wearer goes indoors. The ultraviolet radiation in sunlight produces a photochemical reaction in the lenses, such that an absorption band in the visible part of the electromagnetic spectrum changes dramatically in strength or wavelength. Thus the color change persists for a time even when the light changes.

Hackmanite Color States
Hackmanite Color States

A similar photochromism is exhibited by a gemstone called hackmanite, a variety of sodalite. First discovered in Greenland in 1896, hackmanite is pale to deep violet when first mined. But the color fades quickly to grayish or greenish white when exposed to sunlight. It returns to its original color when placed in the dark for an extended period of time or when exposed to shortwave ultraviolet light.

Hackmanite from Greenland and Quebec changes from pink or violet to white when exposed to sunlight. Hackmanite deposits from Afghanistan and Myanmar change color in the opposite direction - they change from creamy white to pink-red or violet in sunlight. The tenebrescence can be repeated indefinitely. However, heating the gem apparently destroys the photochromism permanently.

Hackmanite was named in honor of the Finnish geologist, Victor Axel Hackman (1866-1941). Hackman was a professor at the University of Helsinki and a geologist with the Finnish Geological Survey.

  • First Published: February-01-2010
  • Last Updated: January-23-2019
  • © 2005-2019 GemSelect.com all rights reserved.
    Reproduction (text or graphics) without the express written consent of GemSelect.com (SETT Company Ltd.) is strictly prohibited.
Pinterest Board Names
More Shapes
Popular Gemstones
  • Sapphire
  • Emerald
  • Ruby
  • Aquamarine
  • Zircon
  • Opal
  • Topaz
  • Tourmaline
  • Garnet
  • Amethyst
  • Citrine
  • Tanzanite
All Gemstones (144)
A B C D E F G H I J K L M N O P Q R S T V Z
  • Actinolite Cat's Eye
  • Agate
  • Agate Geode
  • Almandine Garnet
  • Amazonite
  • Amethyst
  • Ametrine
  • Ammolite
  • Andalusite
  • Andesine Labradorite
  • Apatite
  • Aquamarine
  • Aventurine
  • Beryl
  • Black Opal
  • Bloodstone
  • Boulder Opal
  • Calcite
  • Carnelian
  • Cat's Eye Apatite
  • Cat's Eye Aquamarine
  • Cat's Eye Augite
  • Cat's Eye Gemstones
  • Cat's Eye Moonstone
  • Cat's Eye Opal
  • Cat's Eye Scapolite
  • Chalcedony
  • Charoite
  • Chocolate Opal
  • Chrome Diopside
  • Chrome Tourmaline
  • Chrysoberyl
  • Chrysocolla
  • Chrysoprase
  • Citrine
  • Color-Change Diaspore
  • Color-Change Fluorite
  • Color-Change Garnet
  • Color-Change Sapphire
  • Coral
  • Demantoid Garnet
  • Dendritic Agate
  • Diamond
  • Druzy Amethyst
  • Druzy Azurite
  • Emerald
  • Enstatite
  • Fire Agate
  • Fire Opal
  • Fluorite
  • Fossil Coral
  • Garnet
  • Golden Beryl
  • Grandidierite
  • Grossularite Garnet
  • Hawk's Eye
  • Hematite
  • Hemimorphite Druzy
  • Hessonite Garnet
  • Hiddenite
  • Howlite
  • Idocrase
  • Imperial Topaz
  • Iolite
  • Jade Gemstones
  • Jadeite
  • Jasper
  • Kornerupine
  • Kunzite
  • Kyanite
  • Labradorite
  • Lapis Lazuli
  • Larimar
  • Malachite
  • Malaya Garnet
  • Mali Garnet
  • Maw-Sit-Sit
  • Moonstone
  • Morganite
  • Moss Opal
  • Mother of Pearl
  • Mystic Quartz
  • Mystic Topaz
  • Nuummite
  • Obsidian
  • Opal
  • Opal Doublet
  • Opal in Matrix
  • Pearl
  • Peridot
  • Pietersite
  • Prehnite
  • Pyrite
  • Pyrope Garnet
  • Quartz
  • Quartz Cat's Eye
  • Quartz With Marcasite
  • Rainbow Moonstone
  • Rainbow Pyrite
  • Rhodochrosite
  • Rhodolite Garnet
  • Rhodonite
  • Rose Quartz
  • Rubellite Tourmaline
  • Ruby
  • Ruby in Fuchsite
  • Ruby-Zoisite
  • Rutile Quartz
  • Sapphire
  • Scolecite
  • Seraphinite
  • Serpentine
  • Sillimanite
  • Sillimanite Cat's Eye
  • Smithsonite
  • Smoky Quartz
  • Snowflake Obsidian
  • Sodalite
  • Spectrolite
  • Spessartite Garnet
  • Sphalerite
  • Sphene
  • Spinel
  • Star Diopside
  • Star Garnet
  • Star Gemstones
  • Star Lemon Quartz
  • Star Moonstone
  • Star Rose Quartz
  • Star Ruby
  • Star Sapphire
  • Star Sunstone
  • Strawberry Quartz
  • Sugilite
  • Sunstone
  • Tanzanite
  • Tiger's Eye
  • Tiger's Eye Matrix
  • Topaz
  • Tourmaline
  • Tsavorite Garnet
  • Turquoise
  • Variscite
  • Zircon
Main Categories
  • New Arrivals
  • Gemstone Lots
  • Calibrated Gemstones
  • Gemstones By Piece
  • Top Grade Gems
  • Matching Pairs
  • Cabochon Gemstones
  • Drilled Gems, Briolettes and Beads
  • Birthstones
  • Gemstone Carvings
  • Fancy Gemstones
  • Star Gemstones
  • Unheated Sapphire
English speaking customer support only

Toll Free - USA & Canada only:
1-800-464-1640

International:
+66-39303404

Save Money
No shipping Fees for Additional Items!
$8.90 Worldwide Shipping

Update Translation
 
Current Value
New Value
GemSelect Gemstones
X Close Window
Colored Gemstones
X Close Window
Colored Gemstones
X Close Window
Colored Gemstones
Size and Weight

Gems are always measured in Millimeter (mm)

Dimensions are given as;
length x width x depth,
except for round stones which are;
diameter x depth

Select gems by size, not by weight!
Gem varieties vary in density, so carat weight is not a good indication of size

Note: 1ct = 0.2g

Size Comparison Chart