Gem fluorite from Illinois

This specimen was covered in pitch black bitumen when I obtained it. After several weeks of soaking in organic solvents the true glassy nature of the specimen emerged. A stunning color zone specimen of optical grade fluorite from the most famous mine for such in the United States - the Minerva #1 mine, Cave in Rock, Illinois.

Category:

Science & Technology

Tags:

• mineral
• specimen

[johntveev]

What you have seen are the cleaved octahedrons of fluorite. Fluorite has what is known as perfect cleavage in four directions. This allows people to easily remove corners of crystals to make perfect octahedrons. These are then referred to a crystal fragments and not true crystals.

[TheCaptainLulz]

those look far more like calcite rhombs than fluorite. Hope you didn't get gyped.

[johntveev]

Hi

The crystal form is cubic. Calcite would be rhombic and nowhere near as glassy as these are. There is also no recorded occurrence of blue calcite from Illinois with violet phantoms...Did not get gyped as you put it.

[TheCaptainLulz]

Cool! Ive only ever seen them as octahedrons so I was assuming that was their structure. beautiful sample!