Calcite variety Iceland Spar, optical and otherwise

And Calcite Balls

China

Flats of calcite cleavages. They can be used to demonstrate the optical property of double refraction and cleavage (rhombohedral cleavage). Each flats contains either 54, 35 or 24 specimens each. The more the pieces per box the smaller the specimens. Each interior box has “Double Refraction” stamped in the bottom of the box that can be used to see the double refraction. The cost per flat is $20. The flats with 24/flat pieces measure about 1.75 inches in diameter, the 35’s are about 1.5 in diameter and the 54/flat=1.25 in.

In the 15^th and 16^th centuries all minerals that had good cleavage were called spar by the miners. This included minerals like calcite, barite, gypsum, fluorite etc. Only bit by bit as the science of mineralogy developed was it realized that the term spar included a number of different kinds of minerals. Haüy, the famous French mineralogist in the 18^th century noticed that calcite cleavages would break down into smaller and smaller cleavages with exactly the same angles and this led to his speculations about the fundamental nature and atomic structure of minerals. Once you get you head dialed into the angles of the cleavage breaks you can look at specimens with broken massive calcite on it and identify it with a high degree of certainty. Once in a while you will be fooled if the mineral is dolomite, magnesite or one of the other rhombohedral carbonates. A drop of hydrochloric acid (pool acid) will cause the calcite to bubble like hell and the others will be more restrained in their reaction with the acid. The optical calcite we are selling is not all that clear, just clear enough to demonstrate the optical effect., but it is very inexpensive. Completely clean calcite of optical grade will sell for more than $1000 per pound in the larger sizes and even small clean pieces will bring more than most people want to pay for a demonstration piece. There is still a good demand today for good clean pieces of optical grade calcite for use in various optical devices and this is what drives up the price of really clear pieces of calcite. Historically the first substantial source of optical grade calcite was from the Helgustadir Mine on Eskifjord in Iceland. It has been closed for many years and much of the worlds supply comes sparingly from Mexico and Brazil.

The calcite balls measure from about 3 to 6 inches each and range in color from white to amber and some that are a very pale green. They are all translucent, some more than others. The prices range from $3 to $6 a pound depending on size and quality. A three inch sphere weighs about 1.4 pounds, 4 inch = 3.3 lbs, 5 inch = 6.4 lbs, and a 6 inch sphere weighs a little over 10 pounds.

We encourage our customers to come and visit our warehouse because there is more stuff here than we can possibly tell you about. Check out our web site if you would like to access the recent arrivals list. Click on the New Stuff link at the top of the page.

Jewel Tunnel Imports, 13100 Spring St. Baldwin Park, California 626-814-2257 online at jeweltunnel.com

ORDERS 1 (800) 999 4584 10am – 5pm