Thursday, 30 May 2013

Ardnamurchan Volcano.

Visitors arriving in Ardnamurchan by car, after 25 miles of twisting single track road through beautiful woodland emerge at a viewpoint at Camus nan Geall. This is the first view of the volcanic rocks of Ardnamurchan.
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Ahead can be seen Ben Hiant. This is sometimes mistaken for the volcano, it is in fact a series of rock layers starting from pre-cambrian metamorphic rocks, sedimentary layers and topped with basalts and a dolerite lateral intrusion (think sill) emplaced into rocks now eroded so that it is now the top of Ben Hiant. This last interpretation is the result of research only recently published. 

Volcanoes in this area, or at least the centres of them, tend to be lower lying areas of ground. Loch Ba on Mull, Loch Coruisk on Skye and Glencoe are all volcanic centres which are now valleys. Depressions originating from caldera collapses allowed glacial valleys to form and resulted in the glacial landscape you see today. Ben Nevis is an exception, also a volcano and site of a caldera collapse. 

The Ardnamurchan volcanic centre is again low ground, surrounded by the world renowned  'Great Eucrite'. The center itself is a small intrusion rising from boggy ground  (waterproof boots required). This is best reached from the Kilchoan to Sanna road, 1/2 mile before Achnaha. There is a quarry set slightly above the road on the right if you are heading towards Sanna. There is a short length of fence here. There is parking room for about 4 to 5 cars in the quarry. A track that leads to the abandoned village of Glendrian leaves the quarry on the Sanna side, and it is worth following this. There is a deer fence across your route, and an access gate is provided on this track. Just through the gate leave the track and bear left, you should be able to see where others have walked. The centre is the small rise about 200 meters in front of you.


It is an easy short walk and the view from the center is well worth it, especially in clear fine weather. As well as a magnificent view of the crags of the Great Eucrite surrounding you on all sides, the Isles of Eigg Rum and Skye can be seen, and also the Outer Hebrides on a clear day.

Saturday, 25 May 2013


 After several years of living not too far from Staffa I finally made it to the island. Previous visits having been thwarted by the weather, or lack of proper planning on my part. I must say it was worth the wait. Pictures do not do justice to the atmosphere of the place, and the allotted hour ashore was much too short. Below are some zoomable images, click on the  icon, bottom left of the picture to get a larger view which you can zoom in and drag.

This is the well known view of the entrance to Fingals Cave. The columns are larger than I expected, and a matt intense black, not quite the usual basalt black, and contain a few zeolites. Access to the inside of the cave is along the right wall.

Just before landing from the boat you pass a remarkable set of columns, known as Am Buachaille, or the herdsman. Aligned from vertical to horizontal with a groove in the centre, it challenges interpretation using the usual thermal gradients etc. The clear water shows a deep channel of water between, possibly a collapsed cave at one time?

Finally a view from the top of the island looking north. The headland shows two layers of basalt columns with a more normal flow between, the whole emplaced on a bed of volcanic ash.

Thursday, 23 May 2013

New Online Store -

As mentioned in a previous blog Geosec's new store is now LIVE! It can be found at
Selling slides started as a bit of an experiment in 2004, and ebay was an easy way to get started. Ebay has changed quite a bit in the nine years since, becoming increasingly restricting and expensive for sellers. Another 'Ebay Improvement' is scheduled for August, it seems to be an improvement to allow for increased seller fees in my (admittedly somewhat jaundiced) view. Time has come for a change. has taken a while to set up, as with any new software it takes a while to get to know, which boxes need to be filled and which can be safely ignored. I hope it is fully functional, time will tell. If anyone finds a fault please let me know, and I will try to fix it. 

On other matters Geosec has been assisting to host a geology tour group from Germany. Visits to Iona, Staffa, Mull, as well as Ardnamurchan. I am always happy to show off our outstanding geology, this area can compete with anywhere in the world, and beat most. The group seemed suitably impressed and the weather joined in by providing a sample of every type normally enjoyed here, often in very quick sucession.

Saturday, 18 May 2013

Iona Silverstone

The island of Iona is about 1km off the south west tip of Mull. it is world famous for its religious significance as one of the earliest centres of Christianity in Britain. Among geologists it is also known for being a source of Marble from a quarry on the southern end of the island. Less well known is another outcrop on the western side. This is different from the southern marble as it contains phlogopite mica. This gives the stone from here a "sparkle" and is known as Silverstone.
The outcrop is small and difficult to find. The marble does not occur in large slabs so this area has been little worked. It is quite distinct from any other marble I know. It contains Serpentine (from forsterite), diopside, brucite, and phlogopite in a calcite matrix.
Directios to the site can be provided for anyone interested in visiting it, please contact me via my contact page on It is a fine walk in good weather, from the ferry you need to allow 4 hours for the round trip, as there is plenty of interesting geology (lewisian) and to distract you, and beautiful views to photograph.

Wednesday, 8 May 2013

A wider audience....

To view Thin Section slides in the usual way requires a special microscope, equipped with polarising filters and other refinements not normally found on standard microscopes. These microscopes are not cheap, neither are the thin section slides themselves. Over the past few years Geosec has been trying to find ways to spread the interest in and enjoyment of viewing our slides, to people who do not have access to a microscope and slides.

Photographs are the usual means, but are limited in how much they can convey. There is no movement or change of colour, you cannot 'explore' the slide by moving around it and trying different focus and other settings.

At Geosec we are currently experimenting with video, zoomable pictures and other ideas as much as time permits when not actually making the next batch of slides for sale. An interactive software program, the Geoscope, was tried, but ran into problems with the web browser programs that the program ran in, being automatically updated and stopping it working. 

Ammonite from Madagascar 

So, still work in progress....

Monday, 6 May 2013

Last postings and camera information

As mentioned before there will now be a temporary lull in postings. I will be spending some of the time in publishing on the Geosec Slides website more high resolution images of thin sections.

I now have more than 100 of these waiting for processing, and intend to add descriptions of the minerals, to the best of my abilities. The aim is to aid you, the buyers and anyone interested in minaralogy, to understand what you see. The usual name for these images are photomicrographs, i.e. photographs taken through a microscope. This is not exactly correct in this case. No microscope is involved, the camera is a Canon EOS 60D and the lens a Canon 60mm macro (1x). Polarizing lenses (linear not circular) are mounted either side of the slide.

The advantage of this is the wide field of view, about 20mm, which enables most of the specimen to be photographed. Using a microscope with the lowest power objective usually available, 4x, gives a field of view of about 6mm. This is fine for closeups of individual crystals, but does not give an impression of the specimen as a whole.

Sunday, 5 May 2013

Vesuvius Lava 
GEOSEC. Future plans as of 5th May 2013.

As you may have noticed the number of slides offered for sale has reduced recently. This is only temporary, and there are a number of reasons.

Firstly I am assisting with a geology group who are touring the area, and will be occupied full time with this all next week. 13th to 22nd. Although I will still be here, burglars please note, I will not have time to manufacture anything.

Secondly, much of my machinery is in much need of some maintenance. The machines get used with only minimal servicing for months without break, and some are now urgently requiring attention.

Finally, I am working on a couple of projects, high resolution photographs, movies, and website http://www, development. I am also reviewing how the slides are sold, I have relied much on ebay in the past, and I will still be using it in the future, but there may be alternatives that are more appropriate and can be offered as an alternative. Follow this blog for more information.

Rob Gill.

Saturday, 4 May 2013

Welcome to Geosec's Blog.
This blog will provide current information for Geosec Slides. Thin section geology (petrology) microscope slides produced here in Achnaha. More information about Geosec Slides can be found by clicking HERE