The Scottish Islands with photographs of |
Minerals of the Scottish Isles Introduction - Minerals of Arran |
The Scottish Islands with photographs of |
Minerals of the Scottish Isles Introduction - Minerals of Arran |
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SITE LINKS
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ISLE of ARRAN The island of Arran, with a population of over 5,000, is situated in the Firth of Clyde, and lies much farther south than the other Tertiary volcanic islands and is therefore closer to the more densely populated areas of Scotland. Main access is by a regular ferry service from Ardrossan on the Ayrshire coast. A popular island, it is often termed "The Scottish Highlands in miniature". With a diameter of about 20 x12 miles, it has an interesting geology that encompasses metamorphic and sedimentary rocks from the Cambrian to Triassic eras. In addition, it has undergone episodes of Tertiary plutonism and more recently, in geological terms, glaciation. As a result, the island regularly attracts geological field courses for students, as does the Isle of Skye. The Northern Arran Pluton dominates the island, with Goat Fell, the granitic remains of a Tertiary volcano, its highest peak. There is also a subsidence volcano on the island but, unlike other Tertiary volcanic centres on Scotland's west coast, Arran is virtually devoid of lavas. |
SMOKY QUARTZ & ORTHOCLASE below: ORTHOCLASE- Goat
Fell area, Isle of Arran. |
| It is reckoned a covering of 2,500
meters of this material was removed by glacial erosion
during the last Ice Age. Therefore, glaciation has
moulded much of the island's present-day scenery. Mineral collecting is centred on the Northern Arran pluton - the granite of Goat Fell and surrounding peaks. Small, miarolitic cavities in the granite can yield small, smoky quartz crystals as well as beryl (aquamarine) and topaz - the latter unfortunately as cleavages. Other minerals found include allanite, fergusonite and zircon. Fluorite is another possibility, but has yet to be found "in situ". There is also an old barite mine, to the north of Brodick and zeolites have also been recorded on the island. The island had a reputation for agates, but the localities appear exhausted, though ccasionally, agates may be washed ashore from elsewhere. Finally, there is also a small skarn-type mineral occurence on the island. |
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Recent finds on the island have included some very fine feldspar (orthoclase) crystals and smoky quartz. The quartz is mainly the very dark/ black "morion" variety. Crystals found are generally small, to a few centimeters and translucent. The feldspar crystals have a propensity for multiple and complex twinning and is probably the orthoclase member of this silicate mineral group. The cream-coloured crystals are of good quality, are generally lustrous and fresh, showing minimal signs of etching. right: SMOKY QUARTZ - Ben Tarsuinn, Isle of Arran. A 16 mm transparent, pale smoky crystal. |
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ORTHOCLASE |
ISLE of MULL Off the Scottish mid-west coast, is the Isle of Mull with a population of over 5,000. Access is by ferry from Oban throughout the year and, seasonally, from other sites on the Ardnamurchan Peninsula. Volcanic rocks dominate the island and are the vestiges of a Tertiary volcano (Ben More). Like the Isle of Skye, zeolites are found in the basalt lavas, but are less-common, despite the lavas being of greater thickness on Mull. Agates are found, but they generally lack the colour of their Devonian counterparts from elsewhere. Some of those found on the island contain micro-pyrite crystal inclusions. In xenolithic inclusions in the lavas, the rare mineral, mullite, occurs as pinkish-lilac patches and as crystals. The mineral's name betrays the type locality for the species. The island is also the type locality for the equally uncommon tobermorite. Recently, interesting minerals have been found in proximity to intrusive rocks, including prehnite and stilbite. In similar paragenetic circumstances, in xenoliths, corundum "sapphire" variety, is also found, as well as spinel. The sapphire crystals - first found 100 years ago - are uncovered as generally small and/or irregular in shape. Of a fairly rich colour and transparency, they are not normally of gem-quality as a result of the many inclusions and/or flaws they contain. |
SCOLECITE -
Ben More, Isle of Mull. Despite the Isle of Skye having a proliferation of zeolite mineral species, the Isle of Mull probably supplies the best scolecite examples in Scotland. The locations occur around Ben More.. Hydrothermal mineral veins are almost non-existent on the islands. One exception occurs on the Isle of Islay, where some trials for copper mineralization were made. |
PUMPELLYITE |
CORUNDUM - (Sapphire
variety) |
CORUNDUM - (Sapphire
variety) |
| STAFFA Staffa, a tourist attraction of major geological interest, is just off the west coast of the island of Mull. In the spring and summer months, sailing trips can be made to visit and land - weather permitting! The cave became immortalized after the German composer, Felix Mendelssohn, on one of his many trips to Britain. He was inspired by it to write his well-known Hebrides Overture, known as "Fingal's Cave", between 1830-1832. |
FINGAL'S CAVE - Island of
Staffa. |
RUM (Rhum) This small island with over 20 inhabitants, is a few miles south of Skye, and is owned by the National Trust for Scotland. Permission to collect MUST be sought beforehand. Of interest to mineral collectors are the agates associated with the Tertiary volcanic rocks of the island - particularly on the coast. More recently, rare platinum minerals have been identified in the ultramafic rocks of the island. |
OUTER HEBRIDES
This extended island group forms a bulwark to the Atlantic Ocean and has a total population of over 26,000. Access is by ferry service or by air link to Stornoway. Unlike the other major islands off Scotland's west coast, the islands of the Outer Hebrides are entirely devoid of Tertiary volcanism. In contrast, the rocks are Lewisian in age - Pre-Cambrian era - and are amongst the oldest in the United Kingdom. They typically contain some of the commoner mineral species, though collectors, in recent years, have unearthed some very much rarer and exotic minerals. Mineral occurences include the Chaipaval area for muscovite and other much less common species. On Harris, a find of corundum - (sapphire variety) attracted some media attention a few years ago and some fragments from the find were cut and facetted into gemstones. These are now on display at the Royal Museum of Scotland in Edinburgh. |
MUSCOVITE - Chaipaval,
Lewis, Outer Hebrides. The rejection of creating a large quarry on the island of Harris at Lingerabay, with the prospect of finding some interesting material in future years will no doubt disappoint prospective collectors. Nevertheless, the decision must be weighed against the destruction of the natural beauty of the landscape. Prospects for wind farms have suffered the same fate. It is to be hoped that other prospective mineral sites may well be uncovered without such disturbance being foreseen. |
| SHETLAND & ORKNEY
ISLANDS Immediately north of John O'Groats, on the north-east tip of the Scottish mainland, are the Orkney Islands. Composed almost entirely of Devonian sandstone (continental Old Red Sandstone), minerals do occur here but are much more restricted in nature. Farther north again, are the Shetland Islands, a group of islands with historical Scandanavian connections and currently a major offshore centre for the North Sea oil industry. Here, there is a greater variety in geology with metamorphic rocks pre-eminent. As a result, there are several interesting mineral occurences - though all not necessarily of collector quality. Minerals include chromite in serpentine, talc, "kammererite" (chromian-rich clinochlore), uvarovite, anthophyllite, kyanite and staurolite. Hydromagnesite and nakauriite have also been found. In the past, talc has been commercially exploited from several occurences on the island and these sites may also afford some interesting associated mineral species. Nickel species can also be found. Recently, rare microscopic platinum minerals have been recorded on the island of Unst. Indeed, there is even the prospect of mining to exploit this important element. |
MAGNETITE - Mainland,
Shetland Islands. |
References © Minerals of Scotland - 2008. |
