Optical Calcite Crystal Value Guide

Optical Calcite, famously known as Iceland Spar, is a prized mineral specimen celebrated for its unique double refraction property first documented in 1669. Its historical significance as a potential Viking navigational tool for locating the sun makes it a compelling piece for both science enthusiasts and mineral collectors.

What affects the value of Optical Calcite Crystal?

• Clarity and transparency, with 'water-clear' specimens commanding the highest prices.
• Size and weight of the raw specimen, with larger rhombs reaching the $50 range.
• The presence of internal rainbows or inclusions that can enhance aesthetic appeal.
• Structural integrity, as specimens without significant bruising or internal fractures are more valuable.

How to Identify Optical Calcite Crystal?

• Check for the characteristic rhombohedral cleavage which creates slanted, box-like crystal shapes.
• Verify the 'double refraction' effect by placing the crystal over a line of text to see if the image appears doubled.
• Look for high transparency and a glass-like luster typical of quality Iceland Spar specimens.
• Test for a Mohs hardness of 3; the surface should be easily scratched by a copper coin or knife.

History of Optical Calcite Crystal

Optical calcite, or Iceland Spar, has a fascinating history. Its double refraction property was first described by Christiaan Huygens in 1669, leading to foundational discoveries in optics and light polarization. Historically, Vikings are believed to have used it as a navigational aid, allowing them to locate the sun on cloudy days due to its ability to polarize light. Today, it is valued by collectors, mineral enthusiasts, and those who use crystals for their metaphysical properties.