1 left

calcite - teaching hand specimen of unusual naturally-brown calcite

$ 7.50

This calcite is recrystallized from a limestone in contact with a granitic intrusion. The brown color is unusual and is derived from iron in the limestone that was released by the metamorphism. It effervesces in dilute hydrochloric acid (muriatic acid is the same) as does all calcite.

The crystals of this calcite are interlocking, so it does not cleave into large rhombs, though individual specimens show cleavage faces in several directions. The blue, green and variously wild-colors of the calcite you see being sold at rock shows and shops are an artificial dye. The brown in this calcite is entirely natural.

Brown calcite is an interesting challenge to students who have been introduced to common white or light gray calcite. The rhombohedral cleavage is less important than the effervescence in dilute hydrochloric acid, and it's Mohs scale hardness of 3, which means you can't scratch it with a fingernail, but you can scratch it with a penny to confirm the identification.

Select a specimen: You can select a specimen by telling us what is in the photo with it, a blue or black and silver pen, a black mechanical pencil or one of those plus some number of coins, or you can let us make the selection.

These specimens ship in a small flat rate box unless combined with other purchases. Click > Shipping < for shipping rates. Use back button to return to this page. 

The photo is representative of what we ship.

Making multiple purchases? Click on the "combine shipping" button in the shopping cart. We'll send an invoice with combined shipping. A link in that invoice will bring you back to checkout, no hassle.