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 # 3LOCM04180455
Very Rare 269g Lavender
Optical Calcite from Madagascar

$118.40
Very Rare A Grade 269g Lavender Tint Clear Optical Calcite from Madagascar

We were happily surprised in our never ending search for quality Optical Calcites when we found these Optical
Calcite Crystals from the Mahajanga Province of Madagascar.  We have sold many Optical Calcite Crystals
over the past few years from Mexico, China and Brazil. The most popular so far have been the Brazilian
crystals that are polished with beveled edges.  The Optical Calcite crystals from Madagascar are a new find
and are not known to most collectors... yet that is... we are sure they will become highly sought after very
quickly. Madagascar Optical Calcite crystals are the clearest of them all and some have very bright rainbow
reflections.  Quite a few have a stunning subdued Lavender tint.  Of all locales, these are hands down the
rarest. Excellent Birefringence.

This specimen measures 2.23 x 1.73 x 1.46 inches (56.8 x 43.9 x 37.3 mm) across the flats and 3.2 x 2.6 inches (82.1 x 66.7 mm)
across the diagonals This specimen weighs 9.5oz  or 0.59 lb (269g)
Item # A-GBOPTCAL04183939
141g AAA Grade Optical Calcite
from Brazil Polished in
Idar-Oberstein

$198.40
AAA Grade 141g Clear Optical Calcite from Brazil, Polished in Idar-Oberstein
T

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 finest specimen of Idar-Oberstein polished Brazilian Optical Calcite we have
ever been able to find. This piece has the very best clarity that we have ever seen. This specimen is
truly a one of a kind collectors dream.

We had a difficult time deciding whether to offer this specimen for sale, or keep it for our personal collection.

This specimen measures 1.96 x 1.32 x 1.15 inches (49.9 x 33.5 x 29.4 mm) across the flats and 2.63 x 2.13 inches (66.8 x 54.2 mm)
across the diagonals This specimen weighs 4.98oz  or 0.31 lb (141g)
Item # B-BOPTCAL04180474
205g A Grade Polished Optical
Calcite from Brazil

$101.20
A Grade 205g 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 1.81 x 1.74 x 1.37 inches (46.1 x 44.4 x 34.9 mm) across the flats and 2.8 x 2.31 inches (71.4 x 58.8 mm)
across the diagonals This specimen weighs 7.2oz  or 0.45 lb (205g)