Optical Calcite
(aka)    "Iceland Spar"
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Museum Specimens

This variety of Calcite is called "Iceland Spar", which is basically clear cleaved fragments of completely colorless (ice-like)
calcite. Originally discovered in and named after Eskifjord, Iceland. The Iceland spar displays the classic cleavage form of
calcite, the rhombohedron. Iceland Spar is used for optical equipment and during World War II it was an extremely important
mineral that was used in the sighting equipment of bombardiers and gunners. Our specimens come from the locations
currently producing the most interesting specimens for collectors. We are always looking for more locales.

“A secret mine in the mountains west of the Salton Sea contained the only available source of a particular calcite crystal
needed to make the famous “Norden Bombsight”.  This transparent crystal formation is also known as Iceland Spar because
it is found in cavities in the solidified lava of which Iceland is made.  The war in Europe had made shipping in the North
Atlantic very precarious and the United States needed another source of this precious commodity.  The Norden bombsight
was one of the most important military secrets of World War II; it made possible the very accurate European bombing raids
which helped bring the war to a close.  It was so advanced that bombardiers had to take an oath to protect its secrecy with
their lives.  Arthur LaLonde remembers that one of his first assignments in the military was to search, with four other men, the
snowy summit of Mt. San Jacinto for the Norden bombsight carried on a plane that had crashed there.  Locals who worked
the mine remember that it was guarded by Marines and worked around the clock.  The mine is now within the boundaries of
Anza-Borrego State Park, north of the Salton City Borrego Springs highway.”
Source:  The Periscope 2001 - Publication of the Coachella Valley Historical Society

Iceland spar demonstrates the unique property of calcite called birefringence (double refraction). Double refraction occurs
when a ray of light enters the crystal and due to calcite's unique optical properties, the ray is split into fast and slow beams.
As these two beams exit the crystal they are bent into two different angles (known as angles of refraction) because the angle
is affected by the speed of the beams. A person viewing into the crystal will see two images ... of everything. The best way to
view the double refraction is by placing the crystal on a straight line or printed word. The result will be two lines or two words
visible through the calcite. The thickness and the angle of the Calcite determines the distance between lines or text as can
be seen in the photos in our listings. Turning or rotating the calcite increases or decreases the space between the two lines
or words (double refraction) that this mineral is famous for. Different sides of the rhomb give different separation  distances
for the double refraction as well. These are very educational and interesting pieces!
Item # 6-GBOPTCAL101823802
385g A Grade Optical Calcite
from Brazil Polished in
Idar-Oberstein

$299.99
A Grade 385g Clear Optical Calcite from Brazil, Polished in Idar-Oberstein

We were able to procure a few special specimens in our never ending search for
quality Optical Calcites when we found this Optical Calcite Crystal from Mato Grosso
do Sol, Brazil that was ground and polished in Idar-Oberstein, Germany (Deutchland).  
We have sold many Optical Calcite Crystals over the years from Mexico, China,
Madagascar and Brazil. The most popular so far have been the Brazilian crystals that
are polished with beveled edges.  The best of these Brazilian Calcites are the ones
ground and polished by the artisans in Idar-Oberstein. Of all Optical Calcites we have
ever come across, these Idar-Oberstein calcites are hands down the highest quality
clarity with excellent Birefringence.

This specimen is the largest specimen of Idar-Oberstein polished Brazilian
Optical Calcite we have found. This piece has some milky and some excellent
clarity sections. The most birefringent separation view is end to end

This specimen measures 2.6 x 2.3 x 1.4 inches (66 x 60 x 35.7 mm) across the flats and 3.81 x 3.12
inches (96.8 x 79.2 mm) across the diagonals This specimen weighs 13.6oz  or 0.85 lb (385g)
Item # 10-BOPTCAL12185993
244g Polished Optical Calcite
from Brazil

$89.5
0
A Grade 244g Clear Polished Optical Calcite from Brazil

We were able to procure a few special specimens in our never ending search for quality Optical Calcites
when we found this Optical Calcite Crystal from Mato Grosso do Sol, Brazil that was ground and polished in
Brazil.  We have sold many Optical Calcite Crystals over the years from Mexico, China, Madagascar and
Brazil. The most popular so far have been the Brazilian crystals that are polished with beveled edges.  The
best of these Brazilian Calcites are the ones ground and polished with a high quality clarity with excellent
Birefringence.

This specimen measures 2.99 x 2.4 x 1.43 inches (76 x 61 x 36 mm) across the diagonals
This specimen weighs 8
.6oz  or 0.54 lb (244g)
Item # 12-BOPTCAL12180980
21g Optical Calcite Rhomb from
Brazil

$2
1.00
21g Clear Optical Calcite Rhomb from Brazil

We were able to procure a few special specimens in our never ending search for quality Optical Calcites
when we found this Optical Calcite Crystal from Mato Grosso do Sol, Brazil that was cleved in Brazil.  There
are natural imperfections in Calcite rhombs that have been hand cleved. We have sold many Optical Calcite
Crystals over the years from Mexico, China, Madagascar and Brazil. The most popular so far have been the
Brazilian crystals that are polished with beveled edges.  The best of these Brazilian Calcites are the ones
with a high quality clarity with excellent Birefringence. This one has a little milky clear section with the majority
clear with excellent birefringence

This specimen measures 1.61 x 1.34 x 0.59 inches (40.9 x 34 x 14.9 mm) across the diagonals
This specimen weighs (2
1g)
Item # 1-MOPTCAL09186010
26g Optical Calcite Rhomb from Mexico
$10.00
Item # 3-MOPTCAL09186010
23g Optical Calcite Rhomb from Mexico
$8.00
Item # 5-MOPTCAL09186010
19g Optical Calcite Rhomb from Mexico
$7.00
1.64 x 1.37 x 0.56" (41.7 x 35 x 14mm)
1.87 x 1.55 x 0.32" (47.5 x 39.5 x 8.2mm)
1.61 x 1.35 x 0.47" (41 x 34.3 x 12.1mm)
Item # 8-GBOPTCAL10189763
35g A Grade Optical Calcite from
Brazil Polished in Idar-Oberstein

$52.15
A Grade 35g Clear Optical Calcite from Brazil, Polished in Idar-Oberstein
We were able to procure a few special specimens in our never ending search for quality Optical Calcites when we found this
Optical Calcite Crystal from Mato Grosso do Sol, Brazil that was ground and polished in Idar-Oberstein, Germany
(Deutchland).  We have sold many Optical Calcite Crystals over the years from Mexico, China, Madagascar and Brazil. The
most popular so far have been the Brazilian crystals that are polished with beveled edges.  The best of these Brazilian Calcites
are the ones ground and polished by the artisans in Idar-Oberstein. Of all Optical Calcites we have ever come across, these
Idar-Oberstein calcites are hands down the highest quality clarity with excellent Birefringence.

This specimen measures 1.6 x 1.29 x 0.73 inches (40.7 x 32.8 x 18.5 mm) across the diagonals This specimen weighs 1.24oz  (35g)
Item # 11-BOPTCAL12185943
184g Polished Optical Calcite
from Brazil

$79.70
A Grade 184g Clear Polished Optical Calcite from Brazil

We were able to procure a few special specimens in our never ending search for quality Optical Calcites
when we found this Optical Calcite Crystal from Mato Grosso do Sol, Brazil that was ground and polished in
Brazil.  We have sold many Optical Calcite Crystals over the years from Mexico, China, Madagascar and
Brazil. The most popular so far have been the Brazilian crystals that are polished with beveled edges.  The
best of these Brazilian Calcites are the ones ground and polished with a high quality clarity with excellent
Birefringence.

This specimen measures 2.6 x 2.1 x 1.46 inches (66 x 53 x 37 mm) across the diagonals
This specimen weighs 6
.4oz  or 0.4 lb (184g)