Taseq Slope Minerals - The Fluorescent Minerals of Greenland – Part 2
We will divide this blog into a 5 series post with a focus on the following areas:
- Overview of Greenland and the Fluorescent Minerals from this Locality
- Taseq Slope Minerals
- Kvanefjeld Minerals
- Tunuliarfik Minerals
- Kangerlussaq Minerals
A valley separates the Kvanefjeld area and the Taseq Slopes. The Taseq Slopes are expansive, running the entire width of the middle of the complex. Towards the bottom of the slopes there are large boulders that have eroded from the cliffs above. Climbing up, pockets of sodalite, white veins of albite and analcime, and outcroppings of a myriad of other minerals can be observed. Veins within the lujavrite rocks contain fluorescent minerals like sodalite, ussingite, tugtupite, polylithionite, and others.
Tenebrescent gem quality sodalite is often found on the slopes. Tenebrescence is the “color change” caused by exposure to ultraviolet light (usually shortwave). You can read more about tenebrescence here. Both tugtupite and sodalite exhibit this characteristic in varying degrees throughout the complex. One important note of interest: freshly split rocks will often initially show a deep purple color, which quickly fades. While similar to tenebrescence, this is usually a “one-shot” occurrence. It never happens again (unless the mineral happens to be a tenebrescent sodalite or tugtupite). But it is often a good indicator of fluorescence.
There are three areas of interest on the Taseq Slopes: the eastern slopes, middle slopes, and western slopes. Only the western slopes have been extensively surveyed (by H. Sorensen and others in the mid 60’s). This area is noted for the heavy concentrations of beryllium, and produces some fantastic specimens. The middle slopes and eastern slopes both produce great examples of sodalite and tugtupite, along with a myriad of unidentified species.
Taseq Tugtupite – Found both in boulders that have rolled to the bottom and in veins towards the top of the slopes, this variety of tugtupite is quite different from that found on Kvanefjeld. It was first found in the summer of 2002. It consists of a coarse grained pink veining in massive crystals of analcime. Often pieces are associated with non fluorescing aegirine and what appears to be a spotty green fluorescent analcime. Many pieces have vugs where micro crystals of tugtupite can be found. Daylight color ranges from a light pink to deep pink, but not yet found in a gemmy red state as on Kvanefjeld. This material is also usually quite phosphorescent.
Sodalite (Glacial Boulders) – The Narsaq Elv (river) cuts the valley between the Taseq Slopes and Kvanefjeld. As expected, this cut is filled with water worn (and glacier worn) boulders. Many of these boulders are beautifully round pieces of sodalite. When split open, they reveal a coarse grained sodalite mixed with a bright bluish/white fluorescing analcime (per EDS). The brightness of the blue/white fluorescence (shortwave) could be easily mistaken for scheelite. Interestingly, this type of material has only been found in the eroded boulders – not in the cliffs above. The sodalite is usually deeply tenebrescent.
Tugtupite Crystals – The rarest fluorescent find to date was made during the MinerShop 2002 Greenland “Geo-Adventure”. One of that year’s tour members found a boulder of tugtupite on the eastern slopes. When he cracked it open he found a cavity of wonderfully formed tugtupite crystals – a true rarity! Many pieces have micro crystals but this piece was truly remarkable in size. Although not a gemmy red, the tugtupite deepened in color to an intense pink. A coating of what appears to be a uranyl activated green fluorescence covered many areas on the specimens, along with a yellowish glow – perhaps from another associated (unknown) mineral.
Yellow Sodalite – Sodalite is found throughout the complex (probably as common as calcite is on the dumps in Franklin). The finest specimens are gem quality pieces with deep tenebrescence. In the Taseq area a unique variety has been found which appear yellow under natural lighting, distributed in a white albite/analcime matrix. Upon exposure to shortwave UV, the sodalite color deepens to a dark purple – almost black. The resulting contrast of purple against the white matrix offers a striking specimen. Under shortwave these pieces will initially glow a bright orange – only to deepen to a rust color as the tenebrescence sets in. Some, as in the piece shown here. have chkalovite (fluorescent green) and an unknown purple fluorescing (and phosphorescent) mineral associated with them.
Sodalite and Tugtupite Combination – Combination pieces of tugtupite and sodalite are rare and only found in a few areas within the complex. One area on the Taseq Slopes offers up some fantastic specimens. Often these pieces also have what appears to be a blue fluorescing analcime (initial EDS results). Careful examination of many of the spots yielding these minerals will show regions of sodalite at the outside perimeter – perhaps with veins of ussingite and polylithionite. Next will be concentrations of chkalovite and possibly analcime, followed by tugtupite. Some pockets might be only one or two feet across, while others can be huge.
Ussingite is another major mineral found within the complex (of interest to the fluorescent community). It is a fine-grained mineral (similar to quartzite in texture) and ranges in color from white to a deep gem purple. Deeply colored pieces are used for cabochons and can be quite attractive.
The fluorescent properties of ussingite remain a mystery. Many pieces do not fluoresce at all (or very dimly), while others fluoresce orange identically to sodalite. A few fluoresce a brilliant green. Tenebrescent ussingite has not yet been found. Most often ussingite is found associated with chkalovite, polylithionite, sodalite and tugtupite and is a good field indicator of the presence of these other minerals.
Polylithionite is typically found as greenish mica plates covering feldspars throughout the complex. On the Taseq Slopes a bright silver variety of polylithionite is found with fine-grained layers. This variety is as beautiful in natural light and is a brilliant yellow/white under shortwave. Typically the specimens are massive, reaching one meter in diameter, and often associated with tugtupite (which is also quite phosphorescent).
Pink Fluorescent Tugtupite
A very unusual variety of tugtupite can be found on the Taseq Slopes. Unlike those found on Kvanefjeld, it fluoresces a bright pink – not the typical cherry red. The response under longwave is also quite remarkable – a bright orange. The natural color is a deep (almost purple) red. In addition, these specimens are dramatically phosphorescent a bluish white. In many pieces tugtupite crystals are found which are clean and well formed (micros). Also, polylithionite is commonly associated with these specimens.
Tugtupite enclosing Chkalovite
Exceptional specimens of chkalovite (FL blue/green) being replaced by tugtupite have been observed on the Taseq Slopes. These pieces are striking due to the patterns, as well as the very interesting formation. The matrix is analcime and lujavrite; the green FL is unknown but most likely uranyl activated.
The nickname “Fantasy Rock” encompasses a group of rocks found on the Taseq Slope in the Ilimaussaq Complex, Greenland and only in this one locality within the complex. A typical Fantasy Rock usually consists of four basic minerals: tugtupite, sodalite, chkalovite, analcime, and they are always the most color-rich pieces from this exotic, remote locale.
In Fantasy Rocks, you’ll find tugtupite formed as “eyes” around chkalovite. Sometimes this chkalovite is a magenta fluorescence, and occasionally, the chkalovite will be a rare, pearly white. The combination of the two creates a striking appearance. When you find a rock containing these chkalovite “eyes” along with the assemblage of other colors typically found in fantasy rocks, such as bright orange sodalite, green chkalovite, blue analcime, silver polylithionite and sometimes magenta feldspar, the nickname “Fantasy Rock” seems fitting.
There is still a lot of testing that needs to be done in this area. It has only been explored for the last 20 or so years, still many new minerals to be found and identified.