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Tugtupite Tugtupite is a rare beryllium silicate first found at Ilímaussaq. It was thus found in 1957 at Tugtup agtakôrfia along the north shore of Tunulliarfik fjord, but has since been found in small amounts at several locations at Ilímaussaq. Masses to 10 cm across are known, though it is generally found as grains 1-5 mm or at most a few cm across.
In daylight the color ranges from white to pale pink, pink, deep pink, through deep pinkish-red. Small crystals, to several mm in size, are found in some secondary vugs.
These are transparent and colorless to pale pink and fluoresce brightly. The fluorescence of tugtupite is quite variable but, when strong, it is superb: a vivid cherry-red under shortwave ultraviolet; weaker salmon-orange under mid- or longwave ultraviolet. The color produced under shortwave is difficult to render on CRT screens (such as your computer monitor), and may in fact lie outside its range of reproducible colors. It is a memorable and vivid red. The color of the shortwave response may vary: some is red, some pinkish-red, and some reddish-orange. In all cases the shortwave response is strongest. Of these, the brightest response generally comes from darkly colored tugtupite from Kvanefjeld. This material is generally not phosphorescent.
The deeply colored material seems to be found only at Kvanefjeld. It is used as a semi-precious gemstone by local Inuit artisans. Almost no such tugtupite is without inclusion however; in fact most is turbid. It’s typically fashioned into cabochons and takes a good polish. This material is also noticeably tenebrescent. When taken into sunlight, the reddish color deepens; when placed in darkness, the color fades to a paler hue. Some tugtupite from Taseq slope fluoresces a dimmer red under shortwave ultraviolet, pale salmon-orange under longwave, and dim lavender under midwave ultraviolet.
Tugtupite in such samples is pale pink in daylight, but this color will deepen after exposure to shortwave ultraviolet (or the sun). Here the tugtupite typically forms a fine-grained breccia around 1-3 cm euhedra of non-fluorescent analcime. Such specimens present a stunning ‘reverse polka-dot’ appearance under shortwave ultraviolet.
Secondary vugs occur in some of these Taseq samples, and may contain minute (0.5 to 2 mm) crystals of brightly fluorescent tugtupite. Interestingly, much of this tugtupite fluoresces pinkish-lavender under midwave ultraviolet (see photo at right). Tugtupite in these samples also phosphoresces strongly, white or cream, especially after exposure to shortwave ultraviolet. A very fine-grained variety of tugtupite* with unusual fluorescence has been found from at least two other Ilímaussaq locations: under shortwave ultraviolet it fluoresces pinkish-orange, under midwave bright white, and under longwave an apricot-orange. The brightness of the midwave response is exceptional. These samples are also strongly phosphorescent, white to cream.
Interestingly, the rare mineral tugtupite shares much of its crystal structure with ubiquitous sodalite, and the two are occasionally found together in the same sample, making for superb fluorescent specimens. *This material may be an admixture and requires further study. |
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