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Photomicrography > Quartz > with fluid inclusions
First draft: March 4^th, 2015 | Last update: March 16^th, 2016

Enhydro Quartz (more correctly: quartz with fluid inclusions)
Goboboseb Mountains, Brandberg, Erongo Region, Namibia, Africa

Although the term enhydro is often used to describe eye-visible fluid inclusions with gas bubbles in quartz, it actually refers to water trapped in agates. Fluids being trapped during the growth of minerals and gems is quite common a phenomenon, although eye-visible cavities with moving gas bubbles are rarer. Centimeter-size fluid inclusions with gas bubbles are exceptional.

Such fluid inclusions are found abundantly in quartz crystals from Goboboseb. Other names often encountered for this already classic locality are, undoubtedly amongst many others, Xoboxobos, Gobogobos, and Gobobos. Quartz crystals from this locality tend to show very pronounced growth phenomena that reveal themselves as phantoms running parallel to the crystal's terminations.

These predominantly occur under the form of amethyst and the sought-after fluid inclusions. Besides these, also smoky quartz phantoms can be found. Sometimes the specimens also contain iron oxides and other mineral inclusions. The deposit formed some 130 million years ago during the Early Cretaceous, when rifting started the break-up of Gondwana and caused granitic intrusions (Schmitt et al., 2000).

References and items of related interest

Böllinghaus, T. & van der Smit, M. (2007). Prächtige Amethyst-Fensterquarze aus den Goboboseb-Bergen. Lapis Magazine, Vol. 32, No. 6, pp. 37-43 (in German).

Brewster, D. (1827). Notice Respecting the Existence of the New Fluid in a Large Cavity in a Specimen of Sapphire. The Edinburgh Journal of Science, Vol. 6, pp. 155-156.

Cairncross, B. & Bahmann, U. (2006). Minerals from the Goboboseb Mountains, Brandberg Region, Namibia. Rocks & Minerals, Vol. 81, No. 6, pp. 442-457.

Ewart, A., Milner, S.C., Armstrong, R.A. & Duncan, A.R. (1998). Etendeka Volcanism of the Goboboseb Mountains and Messum Igneous Complex, Namibia. Part II: Voluminous Quartz Latite Volcanism of the Awahab Magma System. Journal of Petrology, Vol. 39, Issue 2, pp. 227-253.

Niedermayr, G., Palfi, A. & Wartha, R. (2002). Neue Amethyst- und Rauchquarzfunde aus den Goboboseb-Bergen in Namibia. Mineralien-Welt Magazine, Vol. 13, No. 6, pp. 72-75 (in German).

Niedermayr, G. & Schnaitmann, E.A. (2010). Neuigkeiten aus Namiba. Mineralien-Welt Magazine, Vol. 21, No. 6, pp. 89-96 (in German).

Schmitt, A.K., Emmermann, R., Trumbull, R.B., Bühn B. & Henjes-Kunst, F. (2000). Petrogenesis and ⁴⁰Ar/³⁹Ar Geochronology of the Brandberg Complex, Namibia: Evidence for a Major Mantle Contribution in Metaluminous and Peralkaline Granites. Journal of Petrology, Vol. 41, Issue 8, pp. 1207–1239.

von Bezing, L., Bode, R. & Jahn, S. (2014). Namibia Minerals and Localities. 2^nd Revised & Updated Edition. Bode Verlag GmbH, Salzhemmendorf, Germany, 608 p. ISBN 9783942588133.

More quartz references

Photomicrographs

Legend: FoV: Field-of-View; DoF: Total focusing depth; DF: darkfield; Obl: oblique illumination (fiber optics); Pol: polarising filter before objective; Sh: shadowing; TM: transmitted illumination, UVL: long-wave ultra-violet radiation; UVS: short-wave ultra-violet radiation; X-Pol: crossed polarising filters

Moving gas bubble in a negative crystal - note how the small bubble is trapped
40x (FoV ± 1.5mm) Obl, DF, Pol

Negative crystals without percetible phases are also found although not that often
18x (FoV ± 3mm) Obl, Pol

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