Origin: Sardinia, Italy
Owner: Axel Emmermann
Origin: Santa Eulalia, Mexico
Owner: Richard Loyens
In this photo you are looking on 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.
1 to 2 cm long crystals of dogtooth calcite on earthy matrix under UV light
Origin: Rio Grande do Sul, Brazil
Owner: Axel Emmermann
Calcite under normal light, LW-UV and SW-UV light
Origin: Durango, Mexico
Owner: Axel Emmermann
When exposed to short wave UV, this specimen briefly exhibits the same pink
fluorescence as under long wave UV before turning blue. The fluorescence is
"delayed" for a very short time. FMS member Glenn Waychunas, a professional
mineralogist, has proposed a hypothesis on that wherein UV energy is absorbed
and stored in photochemical reactions involving cerium, which energy later is
passed to europium to produce the delayed blue luminescence. The pink
fluorescence seen under longwave UV appears to be an orange fluorescence
activated by manganese, added to a weaker case of the blue phosphorescence.
There is not yet enough evidence to establish this theory with any certainty.
(Thanks to Doug Mitchell of the FMS for bringing this new theory to our
attention)
These brown rhombic crystals show a tan fluorescence and strong greenish
phosphorescence. Inclusion of organic matter probably causes the fluorescence.
Stereo photo under short wave UV.
origin: Tarstinkal, Pas-de-Calais, France
Owner: Axel Emmermann
Flattened crystals with pyrite and tetrahedrite. The activator is Mn2+
with lead as co-activator. The concentration of manganese is visibly higher
than in the “normal” red fluorescing calcites. The pink daylight colour is
typical for this “manganoan calcite” that also fluoresces under long wave UV.
Stereo photo under short wave UV.
Large rhombic crystals. Here also, the activator is divalent manganese. The
ideal concentration of manganese as an activator lies at about 1%. More than
enough to explain the pink daylight colour o f the specimen.
Origin: Pachapaqui, Peru
Owner: Axel Emmermann
