Gallery 1 - Fluorescent Minerals...
Photographing fluorescent minerals is a separate branch of mineral photography. Axel Emmermann shows and comments a series of pictures of fluorescent minerals from his own collection.
All photographs © Axel Emmermann

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BARYTOCALCITE in calcite, Langban, Sweden Photograph taken under short wave UV. The name 'barytocalcite' is somewhat of a puzzle. It is the recognized name of the monoclinic form of barium-calcium carbonate. It is also the obsolete name of alstonite which is the triclinic form of BaCa(CO3)2. Mixtures of calcite and baryte were also referred to as 'barytocalcite' in the past. Even more confusing is the fact that the actual barytocalcite is often found in a granular form, mixed with calcite. This is the case in the specimen shown in the photograph. The calcite fluoresces red, the barytocalcite fluoresces blue!

CORUNDUM, (var. Ruby) Karnataka State, India Photo under long wave UV. Ruby is a variety of corundum that contains trace-amounts of chromium. The chromium causes the red color of ruby in plain light as well as its red fluorescence.

ZIRCON, Matongo, Burundi Photograph taken under short wave UV. The crystal is full of cracks and fractures due to metamictisation. Zircon is practically always 'doped' with some thorium and/or other radioactive elements. The decay of these atoms generates highly energetic ionizing radiation that is capable of destroying the structure of the crystal in their vicinity. Therefore zircons are rarely found as clear, gem-quality crystals. The mineral's outer shape is preserved but the appearance becomes opaque and dull. According to 'Fluorescence: Gems and Minerals Under Ultraviolet Light', by Manuel Robbins, trivalent rare earths, particularly dysprosium, praseodymium, and europium, are suspected in this fluorescence. Since dysprosium is associated with similar yellow fluorescences, it seems to be the favorite candidate. (Thanks to Doug Mitchell)

WITHERITE, Rosiclaire, Illinois, USA This mineral belongs to the aragonite-group and has an orthorhombic crystal structure. The hexagonal appearance is due to twinning. The central hole in the crystals suggests a pseudo-hexagonal form, rather than a hexagonal one. The photograph was made under short wave UV. The activator of the blue fluorescence is not known to me at the present time.

HALITE, Heringen, Werra, Hessen, Germany This beautiful specimen is composed of well-formed cubic crystals of a size up to 5 cm. The photograph was taken under short wave UV. The strong red fluorescence is most probably caused by the presence of manganese and lead, analogous to the activation mechanisms in most red fluorescing calcite. However, defects in the crystal lattice of halite are known to cause fluorescence too. Without a chemical analysis we cannot be certain about the true mechanism of this quite enthusiastic luminescence.

BARITE, Villers-en-Fagne, Belgium Barite crystals on matrix. The largest crystal is about 5 mm long. This picture was made under long wave UV with an exposure time of about 6 minutes on Fuji film (100ASA). Fluorescence can be due to inclusions of clay or organic material.

ARAGONITE on CALCITE, Jemelle, Namur, Belgium The light source was short wave UV. The image width is 4 cm and the exposure time was 3 minutes. The calcite matrix fluoresces red which is probably due to the presence of small amounts of manganese (activator) and traces of lead (co-activator). The whitish green fluorescence of the aragonite needles cannot be easily explained. Most likely some trace element in the crystal structure is acting as an activator.

META-URANOCIRCITE, Les Brosses, France This is a really beautiful specimen with almost perfect cubic crystals. Don't be misguided by the shape of these crystals, however. The mineral actually is monoclinic! The green fluorescence is quite common in uranium minerals. The photo was made under LW UV.

CALCITE, Santa Eulalia, Mexico In this photo you are looking at the fractured side of a group of calcite crystals under short wave UV. Under daylight the crystals exhibit a dark brown color suggesting the presence of iron- or manganese-ions. It is well-known that the presence of iron in a crystal acts as a fluorescence-killer. However repeatedly during the growth of this group, the supply of iron seems to have been stopped. As a result, the crystals are made up of alternating layers of iron-containing and iron-free calcite. The iron containing areas of the crystals remain dark under UV-radiation whereas the iron-free areas show a strong fluorescence. Another possible explanation for this phenomenon is a zoning of the concentration of manganese in the crystals. To be effective as an activator in calcite, the concentration of manganese must be between well-defined limits. Within these limits manganese acts as an activator, outside of them it is as effective a quencher of fluorescence just as iron. If during de formation of this specimen the supply of manganese was irregular, only the areas of the crystals that have an optimal concentration of it will fluoresce.