Where is Fluorescent Calcite and Quartz found?
Calcite (CaCO3) and Quartz (SiO2)
Got a photo? Identify rocks instantly with the Rockby app
Open the appFluorescent Calcite and Quartz occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Fluorescent Calcite and Quartz
Franklin and Sterling Hill, New Jersey, USA
World-renowned for highly fluorescent minerals, including calcite (red/orange) and willemite (green), often found together in zinc ore deposits.
Terlingua, Texas, USA
Known for fluorescent calcite, often associated with mercury mineralization, exhibiting bright pink to red fluorescence.
Elmwood Mine, Tennessee, USA
Produces excellent fluorescent calcite specimens, typically glowing red or orange, often with associated fluorite and sphalerite.
Various localities in Mexico
Many Mexican mines, particularly in Chihuahua and Zacatecas, yield fluorescent calcite, often in shades of pink, red, and orange.
Iceland
Icelandic spar (a clear variety of calcite) can exhibit strong red fluorescence.
Alpine fissures, Switzerland and Austria
Some quartz from these environments can show blue or green fluorescence due to fluid inclusions or trace elements.
Collecting tips
- Use a UV Light Source. The primary method for identifying fluorescent calcite and quartz is by observing their luminescence under shortwave (SWUV) or longwave (LWUV) ultraviolet light. A good quality, high-power UV lamp is essential. Some specimens fluoresce under both, others only under one.
- Observe Color and Intensity. Note the color and intensity of the fluorescence. Calcite commonly fluoresces red, orange, pink, or blue. Quartz fluorescence is typically blue, green, or yellow and often less intense than calcite.
- Check for Phosphorescence. After turning off the UV light, some specimens may continue to glow for a short period (phosphorescence), which can be another identifying characteristic.
- Perform Acid Test (for Calcite). Calcite will effervesce (fizz) vigorously when a drop of dilute hydrochloric acid (HCl) is applied. Quartz will not react. This test should be done carefully and on a small, inconspicuous area.
- Assess Hardness. Calcite has a Mohs hardness of 3, meaning it can be scratched by a copper coin. Quartz has a Mohs hardness of 7, meaning it can scratch glass and steel. This helps differentiate the two minerals.
- Examine Cleavage/Fracture. Calcite exhibits perfect rhombohedral cleavage. Quartz shows conchoidal fracture and no cleavage.
Quick Check
- Color:
- Variable (white, colorless, various hues) in visible light; specific fluorescent colors (red, orange, pink, blue for calcite; blue, green, yellow for quartz) under UV light.
- Luster:
- Vitreous to sub-vitreous (calcite), Vitreous (quartz).
- Streak:
- White for both calcite and quartz.
Explore Fluorescent Calcite and Quartz
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.