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Origin of the Name Hemimorphite
The word hemimorphic is an adjective used to describe a crystal that has terminations of different shapes at the end of its primary crystallographic axis. Adolph Kenngott knew that hemimorphite was one of just a few minerals that produced hemimorphic crystals. That inspired him to use the name hemimorphite in 1853. Prior to Kenngott’s use of the name, hemimorphite…
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What Is Hemimorphite?
Hemimorphite is a zinc silicate mineral with a chemical composition of Zn4Si2O7(OH)2*H2O. It contains up to 54% zinc by weight and is a minor ore of zinc. Hemimorphite is a common secondary mineral found in the weathered rocks above and around zinc deposits. Most hemimorphite is white, gray, colorless, or brown. Rare specimens with nice crystals and spectacular yellow, bluish green, or…
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Other Luminescence Properties
Fluorescence is one of several luminescence properties that a mineral might exhibit. Other luminescence properties include: PHOSPHORESCENCE In fluorescence, electrons excited by incoming photons jump up to a higher energy level and remain there for a tiny fraction of a second before falling back to the ground state and emitting fluorescent light. In phosphorescence, the…
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Fluorescent Mineral Books
Two excellent introductory books about fluorescent minerals are: Collecting Fluorescent Minerals and The World of Fluorescent Minerals, both by Stuart Schneider. These books are written in easy-to-understand language, and each of them has a fantastic collection of color photographs showing fluorescent minerals under normal light and different wavelengths of ultraviolet light. They are great for learning about fluorescent…
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Practical Uses of Mineral and Rock Fluorescence
Fluorescence has practical uses in mining, gemology, petrology, and mineralogy. The mineral scheelite, an ore of tungsten, typically has a bright blue fluorescence. Geologists prospecting for scheelite and other fluorescent minerals sometimes search for them at night with ultraviolet lamps. Geologists in the oil and gas industry sometimes examine drill cuttings and cores with UV…
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UV Lamp Safety
Ultraviolet wavelengths of light are present in sunlight. They are the wavelengths that can cause sunburn. UV lamps produce the same wavelengths of light along with shortwave UV wavelengths that are blocked by the ozone layer of Earth’s atmosphere. Small UV lamps with just a few watts of power are safe for short periods of…
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Lamps for Viewing Fluorescent Minerals
The lamps used to locate and study fluorescent minerals are very different from the ultraviolet lamps (called “black lights”) sold in novelty stores. The novelty store lamps are not suitable for mineral studies for two reasons: 1) they emit longwave ultraviolet light (most fluorescent minerals respond to shortwave ultraviolet); and, 2) they emit a significant…
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Fluorescent Geodes?
You might be surprised to learn that some people have found geodes with fluorescent minerals inside. Some of the Dugway geodes, found near the community of Dugway, Utah, are lined with chalcedony that produces a lime-green fluorescence caused by trace amounts of uranium. Dugway geodes are amazing for another reason. They formed several million years ago in…
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Fluorite: The Original “Fluorescent Mineral”
One of the first people to observe fluorescence in minerals was George Gabriel Stokes in 1852. He noted the ability of fluorite to produce a blue glow when illuminated with invisible light “beyond the violet end of the spectrum.” He called this phenomenon “fluorescence” after the mineral fluorite. The name has gained wide acceptance in mineralogy, gemology,…
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How Many Minerals Fluoresce in UV Light?
Most minerals do not have a noticeable fluorescence. Only about 15% of minerals have a fluorescence that is visible to people, and some specimens of those minerals will not fluoresce. Fluorescence usually occurs when specific impurities known as “activators” are present within the mineral. These activators are typically cations of metals such as: tungsten, molybdenum, lead,…