UV blocking glasses should always be used when working with a UV lamp for a long time.

Always follow the UV light safety advice described in part III < You may be surprised to learn that some people have encountered geodes with fluorescent minerals inside.

Some of the Dugway geodes, found near the community of Dugway, Utah - US, are lined with chalcedony which produces a lime green fluorescence caused by traces of uranium.

Dugway geodes are surprising for another reason. They formed several million years ago in the gas pockets of a bed of rhyolite. Then about 20 thousand years ago they were corroded by the action of waves along the shore of a glacial lake and carried several miles to where they finally came to rest in lake sediments. Today, people dig up and add them to the mineral collections of geodes and fluorescents.

This spodumene (kunzite) provides at least three important lessons in mineral fluorescence. All three photos show the same dispersion of specimens. The top is in normal light, the center is in short wave ultraviolet, and the background is in long wave ultraviolet.

2) Fluorescence can be of different colors under shortwave waves and longwaves; 3) Some specimens of a mineral will not be fluorescent.

Practical Uses of Mineral and Rock Fluorescence

Fluorescence has practical uses in mining , gemology, petrology and mineralogy. Scheelite, a tungsten ore, typically has a bright blue fluorescence. Geologists looking for Scheelite and other fluorescent minerals sometimes look for them at night with ultraviolet lamps.

Fluorescent lamps can be used in underground mines to identify and trace ore rocks. They have also been used in picking lines to quickly detect valuable pieces of ore and separate them from waste. Many gemstones are sometimes fluorescent, including ruby, kunzite, diamond and opal. This property can sometimes be used to detect small stones in sediment or crushed ore. It can also be a way of associating stones to a mining location. For example, light yellow diamonds with strong blue fluorescence are produced by Premier Mine of South Africa, and colorless, strongly fluorescent blue stones are produced by South Africa's Jagersfontein Mine. The stones of these mines are nicknamed "Premiers" and "Jagers."

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In the early 1900s, many diamond traders looked for stones with strong blue fluorescence. They believed that these stones would look more colorless (less yellow) when viewed in light with high ultraviolet content. This has resulted in controlled lighting conditions for color classification diamonds.

Fluorescence is not routinely used in mineral identification. Most minerals are not fluorescent and the property is unpredictable. Calcite is a good example. Some calcite is not fluorescent. Calcite samples that shine in a variety of colors including red, blue, white, pink, green and orange. Fluorescence is rarely a diagnostic property.

Other Luminescent Properties

As I said earlier, fluorescence is just one of several properties of Luminescence that a mineral can exhibit.

Other luminescence properties include:

Two excellent introductory books on fluorescent minerals :

both by Stuart Schneider. These books are written in easy-to-understand language and feature a fantastic collection of color photographs that show fluorescent minerals under normal light and different wavelengths of ultraviolet light. They are great for learning about fluorescent minerals and serving as valuable reference books.