MINERAL OF THE MONTH: FLUORITE

Welcome to another edition of "Mineral of the Month," where we dive into the world of fluorescent minerals and explore different minerals and their properties. This time, our spotlight shines on fluorite.

Fluorite Fluorescence

Fluorite often times has bright fluorescence under ultraviolet light, revealing bright colors that range from purples and blues to brilliant greens and reds. Fluorite from various localities can display unique characteristics such as fluorescing zoning or daylight fluorescence. Anyone with a fluorescent mineral collection probably has a piece of fluorescent blue fluorite, the most common fluorescent color for this mineral.

Purple Fluorite Crystals

Purple Fluorite Crystals Under Longwave

Rogerley Fluorite and “Daylight Fluorescence”

Rogerley fluorite is a famous type of green fluorite from the Rogerley Mine in County Durham, England. These pieces set the bar for other fluorites on the market, they are simply some of the nicest out there. Under visible light, a nice specimen will contain gemmy emerald green fluorite crystal cubes. Their fluorescence is so intense and bright, that even when exposed to sunlight, the UV from the sunlight will cause a noticeable color change to blue in the green fluorite crystals. We call this phenomenon, Daylight Fluorescence. It’s very cool to see in person. If you have a piece of Rogerley fluorite, take it out in the sunlight and notice the color change.

Famous Green Fluorite from Rogerley Mine 

Fluorescent Zoning in Fluorite

Fluorescent zoning primarily results from variations in the mineral's chemical composition and the presence of trace elements during its formation. Different impurities or changes in the local geological conditions can influence the color and fluorescence exhibited by various zones within a fluorite crystal.

Fluorite Chemical Composition and Physical Properties

Fluorite, scientifically known as calcium fluoride (CaF2), consists primarily of two elements: calcium (Ca) and fluorine (F). In its purest form, it forms a colorless, transparent crystal, but the presence of trace elements can infuse a spectrum of colors into this otherwise clear crystal. For instance, impurities like yttrium, cerium, or rare earth elements can introduce the stunning array of colors that make fluorite so sought after in the world of mineral collecting. This mineral diversity leads to the various hues of purple, blue, green, yellow, and pink that we commonly associate with fluorite.

Fluorite’s crystal structure belongs to the cubic crystal system, a classification shared by minerals like salt (halite) and pyrite. The cubic system, characterized by its symmetrical and box-like crystal shapes, provides the foundation for fluorite's vibrant fluorescence and remarkable transparency.

At the heart of fluorite's crystal structure lies the interaction between calcium and fluorine ions, resulting in a remarkably strong and stable lattice. The fluorine ions are tightly bound to the calcium ions, creating a robust three-dimensional framework. This orderly arrangement is the secret behind fluorite's exceptional clarity and durability.

Cleavage and Hardness: 

Fluorite exhibits four distinct cleavage planes, making it relatively easy to cleave into octahedral fragments. Despite this cleavage, fluorite is not considered a soft mineral. It has a moderate hardness, ranking 4 on the Mohs scale. This property ensures that fluorite can withstand normal wear and tear, making it a good choice for jewelry and ornamental use.

Density and Specific Gravity:

The density and specific gravity of Fluorite are also noteworthy. Its specific gravity typically falls in the range of 3.0 to 3.3, depending on the impurities present. This relatively high specific gravity distinguishes Fluorite from other minerals and contributes to its distinct feel and heft.

A Specimen Containing Clear to Pink Fluorite Crystals

Fluorite’s Fun History

Fluorite's historical roots can be traced back to ancient civilizations, where it was often associated with mystical and healing properties. The ancient Egyptians, for instance, believed that fluorite possessed protective qualities, using it in amulets and jewelry to ward off negative energies and promote harmony. Similarly, in ancient China, fluorite was thought to have the power to reveal truth and enhance spiritual awareness.

In addition to its mystical properties, fluorite's visual appeal also made it a sought-after gem in various cultures. The ancient Romans carved drinking vessels, known as "fluorite cups," from this mineral to appreciate the way it would glow when filled with liquid. These cups were considered not only practical but also beautiful works of art.

Fluorite has also made its mark in architectural history. In Gothic cathedrals, particularly in the stained glass windows of the Chartres Cathedral in France, fluorite was used as a substitute for other precious gems. Its distinctive colors and fluorescence added a unique and ethereal quality to these magnificent works of architecture.

Stay tuned for our next “Mineral of the Month” post, where we explore a new mineral and its occurrence and fluorescence.