Lherzolite mantle xenolith. Eifel Germany

This is a thin section of a mantle xenolith from Meerfelder Maar in the Eifel volcanic complex. A Lherzolite; olivine, orthopyroxene and chrome diopside. Brought to the surface as a nodule within the lavas.

Very limited material availability.

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Gabbro, Flow Aligned Eucrite, Ardnamurchan.

This is a thin section of Eucrite from the tertiary volcanic centre in Ardnamurchan, on the West Coast of Scotland. Famous for its complete ring dyke made of this material (or is it a Lopolith?). It is a gabbro consisting mainly of plagioclase feldspar, classic albite twinning, with large olivine crystals and pyroxene. This is a sample showing alignment of the plagioclase laths. These also show exceptionally sharp twinning. The pyroxene in this slide is interesting as, although it is only about 20% of the minerals by volume, it appears to be one large crystal, larger than the whole sample. This can be seen by the consistent XPL colour and the same extinction position of all the separate parts

More expensive than the standard Eucrite as this material presents certain production difficulties.

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Andesite Tuff. Bodrum, Turkey.

This is a thin section microscope slide of a dark andesitic tuff showing flow structure from the Bodrum region of Turkey. Contains crystals of plagioclase, pyroxene (augite), biotite mica and rock fragments in a matrix of brown volcanic glass. This shows flow structure. Interesting slide.

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Peridotite. Centre 3, Ardnamurchan, Scotland

This is a thin section of a rare volcanic rock, Peridotite. Widely written about, features in all the texts as the ultimate in ultrabasic rocks ( or maybe dunite) but rarely seen in an unaltered form. (relatively common as serpentine). This is from some large (100m plus) xenoliths in a remote part of the great eucrite, centre 3 Ardnamurchan. How and why they are there is a subject for much geological discussion. Slide contains over 50% good sharp olivine crystals with characteristic curved cracks and a small amount of alteration of the edge to Talc. Some augite and secondary chlorite and Plagioclase, well twinned and partial normal zoning, forms the rest of the slide.  Extra special

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Granite / Greisen, Topaz, Zinnwaldite. Germany

This is a thin section microscope slide of Greisen (altered granite) from Zinnwald, Saxony, Germany. From a tin mining area this is an altered granite containing fans of Zinnwaldite (the type locality, a type of mica), very bright colours in xpl, and Topaz of a type known as Pyknite. This shows characteristic basal parting, and some alteration in the cracks. Very Pretty slide.
This slide contains several large topaz phenocrysts, which are fragmented, apart from the natural preexisting basal partings. These topaz have proved difficult to preserve. Slide left very slightly thick for the same reason

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Hornblendite. Achmelvich, Scotland

This is a thin section microscope slide of Hornblendite. A most unusual rock. Collected from what appeared to be a dyke(?)  exposed on the shore at Achmelvich, Scotland. Contains 100% actinolite, silvery pale green in thin section, an absolute riot of colour with crossed polars. The actinolite is composed of short laths and lozenge shaped crystals showing characteristic amphibole cleavage angles. Similar to an illustration p45 Atlas of rock forming Minerals.

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