The Curious Vault 001: Calcite



Tucked away on a high shelf in the collections room of the Museum of Science is a startlingly unique rock specimen. It is white with long jutting crystal arms and made of a fragile mineral called calcite. The piece looks like it comes from completely different planet.

How calcite looks isn’t the only amazing thing about it.  Scientists in England have recently shown that calcite might unlock the secret to invisibility. They even make a paperclip disappear! By using the light that reflects off two specially made pieces of calcite, they are able to make the object behind them undetectable. Harry Potter’s invisibility cloak could one day happen due to this amazing mineral.

Calcite Detail

If you want to learn more about calcite, the Miami Mineralogical and Lapidary Guild is the best resource in town. They are a quirky and fun group, dedicated to all things rock-related. Founded in 1955, the Guild has been an affiliate study group with the Museum for those interested in rare or semi-precious stones, cutting and shaping them, and most importantly learning about them.  They are very friendly, and welcome all visitors to learn about their unique hobby.

The members of the Guild explained to me that you can identify the specimen as a calcite because of its “habits”.  Simply put a habit is the rock’s shape, or in this case, the crystal arms that jut out. How the habits are formed depend on where the rock was made. This particular specimen was found in Wisconsin and its habits come from the precipitation of either ground water or surface water piling on top of each other and hardening over the course of millions of years. The water drips and dries leaving coatings with small particles of the limestone walls that build up and form the calcite.

Snowy River Cave (Image Source:

One of the more fascinating places calcite can be found is the Snowy River Cave in New Mexico. There is a dry underground riverbed of white calcite, much like the Museum specimen. Only 9 miles of the cave has been mapped and the full extent of the bed is still unknown, but the discovery is one of the most important recent calcite and caving finds in America.

“Nature makes it different every time,“ said the Mineralogical and Lapidary Guild’s Vice President K.C. Foster.  This is an important sentiment for minerals because, like a fingerprint, no calcite is ever the same. Whether an underground riverbed, a composite that can make things invisible, or a beautiful specimen like the one in the Museum’s collection, calcite is an amazing and unique mineral.

The Board of the Miami Mineralogical and Lapidary Guild

The Miami Mineralogical and Lapidary Guild meets the first Wednesday of every month at the Miami Museum of Science. They also set up interactive demonstrations for families and visitors the fourth Sunday of every month from 1-4 p.m.

The Curious Vault is a bi-weekly online cabinet of curiosities featuring objects from the collection of the Miami Science Museum, presented by writer Nathaniel Sandler and Kevin Arrow, Art & Collections Manager. For more information, email


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