| Optical Calcite (aka) "Iceland Spar" |
| SpiritRock Shop |
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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 came from Santa Eulalia District, Mexico
“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
| Item # ISCOC11119180 49g Iceland Spar Clear Optical Calcite $16.95 |
| Item # ISOC11112050 137g Iceland Spar Optical Calcite Rhomb $12.95 |
| 49g Iceland Spar Clear Optical Calcite This specimen measures 1.6 x 1.3 x 0.55 inches (41 x 33 x 14mm) and weighs 1.72oz (49g) |
| 137g Iceland Spar Optical Calcite Rhomb This specimen measures 2.0 x 1.9 x 1.0 inches (51 x 49 x 26mm) and weighs 4.84oz (137g) |
| Item # ISCOC11114350 40g Iceland Spar Clear Optical Calcite $16.95 |
| 40g Iceland Spar Clear Optical Calcite This specimen measures 1.4 x 1.3 x 0.45 inches (36 x 35 x 11mm) and weighs 1.4oz (40g) |
| Item # ISCOC11110280 63g Iceland Spar Clear Optical Calcite $16.95 |
| 63g Iceland Spar Clear Optical Calcite This specimen measures 1.5 x 1.48 x 0.63 inches (39 x 37 x 16mm) and weighs 2.2oz (63g) |
| Item # ISCOC11115350 35g Iceland Spar Clear Optical Calcite $15.95 |
| 35g Iceland Spar Clear Optical Calcite This specimen measures 1.68 x 1.36 x 0.36 inches (42 x 34 x 9mm) and weighs 1.24oz (35g) |
| Item # ISCOC11119570 28g Iceland Spar Clear Optical Calcite $14.95 |
| 28g Iceland Spar Clear Optical Calcite This specimen measures 1.77 x 0.85 x 0.42 inches (44 x 21 x 10mm) and weighs 0.96oz (28g) |
| Item # ISOC12119680 48g Iceland Spar Optical Calcite Rhomb $17.95 |
| 48g Iceland Spar Optical Calcite Rhomb This specimen measures 1.6 x 1.1 x 0.6 inches (40 x 29 x 17mm) and weighs 1.7oz (48g) |
| Item # ISOC12118370 26g Iceland Spar Optical Calcite Rhomb $14.95 |
| 26g Iceland Spar Optical Calcite Rhomb This specimen measures 1.4 x 1.1 x 0.3 inches (36 x 30 x 9mm) and weighs 0.92oz (26g) |
| Item # ISOC12113760 24g Iceland Spar Optical Calcite Rhomb $13.95 |
| 24g Iceland Spar Optical Calcite Rhomb This specimen measures 1.4 x 0.7 x 0.5 inches (36 x 18 x 14mm) and weighs 0.86oz (24g) |
| Item # ISOC12113770 41g Iceland Spar Optical Calcite Rhomb $15.95 |
| 41g Iceland Spar Optical Calcite Rhomb This specimen measures 1.5 x 0.8 x 0.7 inches (39 x 21 x 18mm) and weighs 1.46oz (41g) |
| Notice to Our Customers We will be closed from May 18th through August 15th 2012 to relocate our business. Orders placed during this time will not be shipped until after August 15th. Purchases or Reservations will be honored in the date order they are received. 1st purchaser is served 1st. |