LAPRADORITE SPECIMEN GEM GRADE FROM MADAGASCAR.

ELECTRIC MIDNINGHT Natural stone that has been hand polished and waxed added to get a fine luster.

Labradorite is truly a fascinatingly beautiful mineral which reminds me of black opal. Its a mineral whose charm is not fully noticed and may be overlooked if not viewed from the proper position. Generally a dull, dark looking mineral with no special virtue until the colorful shiller is observed glowing on the surface. Labradorite can produce a colorful play of light across cleavage planes and in sliced sections called labradorescence. The usually intense colors range from the typical blues and violets through greens, yellows and oranges. Some rare specimens display all these colors simultaneously. 

Note the reflection you see is from the light we used to take the picture.

The color display is from lamellar intergrowths inside the crystal. These intergrowths result from compatible chemistries at high temperatures becoming incompatible at lower temperatures and thus a separating and layering of these two phases. The resulting color effect is caused by a ray of light entering a layer and being refracted back and forth by deeper layers. This refracted ray is slowed by the extra travel through the layers and mixes with other rays to produce a light ray coming out that has a different wavelength than when it went in. The wavelength could correspond to the wavelength of a particular color, such as blue. The effect depends on the thickness and orientation of the layers. If the layers are too thick or too thin no color shiller is seen. Also if the viewer does not observe from the precise angle or if light is not supplied from the proper angle then no color shiller is seen. The labradorescence is truly a one of a kind mineralogical experience and must be observed in person in order to truly appreciate its beauty.

Labradorite is a member of the plagioclase series of minerals. The plagioclase series comprises felspars that range in chemical composition from pure NaAlSi3 O8 to pure CaAl2 Si2 O8 . Labradorite is defined at approximately the 50% to 70% CaAl2 Si2 O8 . Labradorite by definition must contain 50-70% calcium to 50-30% sodium in the sodium/calcium position of the crystal structure. All members of the plagioclase series usually display lamellar twinning called “Albite Twinning”. The twinning is caused by a error in the crystal structure during its growth.