THE MINERAL ELBAITE
Elbaite belongs to the group of minerals known as the Tourmalines.
It is the most colorful member of this group.
Elbaite is often cut as a gemstone, sliced into colorful cross-sections or simply appreciated
as natural specimens by millions of rock collectors.
The many varied colors of Elbaite make it arguably the most colorful of the precious stones.
Elbaite contains many variety names based on color.
A beautiful blue variety is called
indicolite (also known as indigolite),
the pink to red variety is called rubellite, the green variety is known as verdelite, while the most famous variety is a pink and green combination called watermelon tourmaline.
Often a specimen can have more than one color zone in the same crystal.
These zones can alternate in color from the inside to the outside or from the top to bottom.
Elbaite is strongly
pleochroic
which means that a transparent crystal will appear darker when viewed down the long
axis of the crystal.
A green or blue Elbaite can appear black when viewed from such an angle.
PHYSICAL CHARACTERISTICS:
- Color is extremely variable with the most common colors being red, pink, green, blue, orange and yellow.
- Luster is vitreous.
- Transparency: Crystals are transparent to translucent.
- Crystal System: Trigonal; 3 m
- Crystal Habit is typically elongated three, and occasionally six, sided prisms.
The terminations can be either a simple to complex trigonal pyramid or flat basal face.
The prism faces are
striated lengthwise.
In cross section, all tourmalines will appear predominantly triangular
in shape with some crystals showing a hexagon when three secondary prism faces are nearly as dominant as the three primary prism faces.
Doubly terminated crystals are hemimorphic meaning that the two ends of the crystal are not exactly alike.
The terminations on a doubly terminated crystal can have different slants to the pyramids on opposite ends.
Acicular and massive forms can also be found.
- Cleavage is absent although there is basal parting.
- Fracture is uneven to conchoidal.
- Hardness is 7 - 7.5
- Specific Gravity is 3.0+ (average)
- Streak is white.
- Other Characteristics: Refractive indices = 1.62 and 1.68 .
- Associated Minerals include those minerals associated with granitic pegmatites and metamorphic rocks
such as
micas,
feldspars,
quartz and even other gem minerals such as
beryl,
garnets,
spodumene and
topaz.
- Notable Occurrences include the San Diego, California area; Brazil; Elba, Italy (where Elbaite gets its name);
Sri Lanka; Pakistan; Maine, USA and Russia as well as many others.
- Best Field Indicators are crystal habit, triangular cross-section, color and hardness.
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