Lapis Lazuli. Afghanistan.

This is a thin section of Lapis Lazuli from Afghanistan. Blue Hauyne/Lazurite often surrounding grains of apatite. Areas of Diopside showing bright XPL colours and twinning/exsolution and rims of secondary alteration minerals. This material does not look particularly blue in XPL, as the sodalite/Hauyne/Lazulite family are isotropic and thus dark in XPL.


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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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Limbergite. Limberg, Germany.

This is a thin section microscope slide of a very rare volcanic rock, Limbergite. From the carbonatite volcanic complex at Kaiserstuhl, in southern Germany. An interesting brown matrix contains titaniferous augite with the usual zoning and magnificent interference colours, olivine with altered rims and fresh centres, some crystals embayed. Outstanding amygdules, filled with zeolites, often different types, sometimes including an unidentified red one.


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Meteorite Impactite Rock. Stac Fada, NW Scotland.

This is a thin section microscope slide of the Stac Fada Meteorite Impact deposit. Initially thought to be a volcanic mudflow this deposit, found within the Torridon sandstone sequence, is now believed to be the 'fall out' from the impact of a massive meteorite about 1.2 billion years ago. The strike is thought to be centred in what is now The Minch, the stretch of water between the North West Scottish mainland and the Outer Hebrides. Impact deposit characteristics have been found in the deposit, buy and check them out for yourself, I must admit to not being an expert in this field.


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Pegmatite, Tourmaline, Topaz. Namibia

This is a thin section of a Pegmatite rock from Spitzkopje in Namibia, Africa. This source is known for it's crystals, especially Topaz. This sample contains mainly Tourmaline quartz epidote and Mica, but does contain Topaz. This is difficult to identify as the optical characteristics are similar to quartz, but close examination will show it. There are over 50 minerals found at this site, so you may find more than I have named.

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Granite Toumaline Pegmatite. Portsoy, Scotland

This is a thin section of Granite Pegmatite from Portsoy, Aberdeenshire, Scotland. This locality is well known for its 'Marble', actually a serpentine. A short distance away are some small granitic pegmatites with very interesting mineralogy. Containing blue tourmaline, rosettes of mica and small garnets in large pink orthoclase  feldspar which has a graphic intergrowth texture with quartz. I am not sure which mica this is, the books say muscovite, but it is unlike 'normal' muscovite both in its field occurrance and its appearance in thin section. Beryl is also sometimes found in this rock.


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Pulaskite. Greenland.

This is a thin section microscope slide of a Pulaskite from Ilimaussaq, Greenland. The donor of this sample, to whom I am most grateful for this and other exceptionally rare rock samples, describes this as representing the least evolved rocks in the Ilimaussaq intrusion, and possible the parental magma from which the other rocks in the intrusion evolved. This sample shows aegirine and ardfedsonite, some unidentified mineral with radiating acicular form and light microcline in a feldspathoid matrix, nepheline and others. The microcline has a most unusual mosaic like twinning.
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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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Essexite. Crawfordjohn, Scotland

This is a thin section of a rare volcanic rock, Essexite. From Crawfordjohn in southern Scotland. A silica poor rock containing large titaniferous (pink) augite crystals with excellent crystal form, showing growth zoning, zoned inclusions, sector zoning and magnificent interference colours. Numerous small but colourful olivine, somewhat fuzzy labradorite laths rimmed with alkali feldspar; apatite and magnetite. See page 97 Atlas of Igneous rocks and their textures. Very Special.


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Dolerite (Scourie Dyke). Lewisian. Scotland.

This is a thin section microscope slide of Scourie Dyke material from Scourie, North West Highlands of Scotland. Thought to be 2390 million years old, (give or take a year or two), cutting even more ancient Lewisian Gneiss, and getting on for half the age of planet earth. Some of the most ancient rocks found anywhere. The Scourie Dykes are world famous. Essentially a dolerite, containing plagioclase, remarkably unaltered, nicely twinned and zoned, some showing curving due to subsequent strain, pyroxene and magnetite both rimmed with hornblende, and a little quartz. Essential part of any serious collection.



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Actinolite in Talc. N.W. Scotland

This is a thin Section microscope slide of a rock from Auctertyre, near Kyle of Lochalsh, associated with the Lewisian (pre cambrian) 'inlier'. Well formed crystals of actinolite in a matrix of very fine grained talc. Very pretty in XPL.


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Chrysocolla, Arizona, USA.

This is a thin section of Chrysocolla with sometimes Malachite, copper ore, from Arizona USA. Banded botryoidal texture showing beautiful growth patterns.  Also some good bands iron mineral at edge (?goetheite) Good material, highly recommended. Some bubbles in the cement in this slide.



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Schist, Garnet mica, Glenborrodale Scotland.

This is a thin section of a Garnet Schist from Glenborrodale on the Ardnamurchan peninsular. Moine Schists form the bedrock underlying the volcanic rocks. This sample is a remarkably clear and interesting example. Mineralogy is what you would expect, Muscovite and Biotite micas, chlorite, recrystalised quartz and garnets, which are particularly interesting as they contain 3 zones and significant internal texture, including evidence of rotation during growth. Clear, colourful and unusual. Recommended.


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Stromatolite. Bolivia.

This is a thin section microscope slide of a fossilised stromatolite from the Bolivia, 2.2 to 2.4 Billion Years old. Shows growth banding and oolites. Excellent example.


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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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Kentallenite. Lochaber, Scotland.

This is a thin section microscope slide of Kentallenite, a rare rock collected from the type location at Kentallen, on the shores of Loch Linnhe, in Scoland. Contains Olivine augite, biotite, and both plagioclase and orthoclase feldspar. Spectacular under crossed filters, the different minerals show up well and are easy to identify except the feldspars, which are a little more challenging. An unusual rock and difficult to classify, probably best called an olivine monzonite. See page 105 Atlas of Igneous rocks, MacKenzie et al. Highly recommended slide , to form part of any collection of Scottish rocks. The photos do not do it justice.


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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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Ultramafic Cumulate. Alaska.

This is a thin section of a ultramafic peridotite cumulate from the Brady Glacier Nunatak, La Perouse intrusion, Fairweather Range, S.E. Alaska USA. An exceptionally good cumulate texture, bright, colourless and totally fresh olivines in plagioclase and orthopyroxene poikilitic textured matrix. The orthopyroxene is in parts gradually altering to red/brown biotite, both parts in the same continuous crystal. Biotite is a hydrous mineral, so water must be present, but the olivine shows no sign of alteration. Highly Interesting.


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