SCOTTISH ISLANDS |
Minerals
of the Scottish Isles Introduction
- Minerals of Arran including
photographs of |
|
Introduction Off the Scottish coast - mainly the west coast - there are several relatively large islands and hundreds of smaller ones. During summer months, pleasure sailors step ashore and "collect" them - a hobby known as "island-bagging". This highlights not just the smallness and profusion of some, but also their relative remoteness. The overall population of Scotland's islands is almost 100,000. These range from the Shetland Islands with over 22,000 inhabitants to those with inhabitants in the single figures. The majority are, however, unpopulated. Access
to them is normally by ferry services, which vary |
SMOKY
QUARTZ & ORTHOCLASE |
The
islands described below are some of the interesting ones
known for mineral occurences. |
As for minerals, many may await discovery on these watery outcrops. Some quarrying, carried out on a limited number of islands in the past, may provide additional interest. Conversely, the prospect of a large super quarry for aggregates on Harris has been halted by the Scottish Parliament on environmental grounds. There are similar projects being considered on Tiree and the Shetland Islands. |
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 A popular
island, it is often termed "The Scottish
Highlands in miniature". With a diameter of
about 20 x12 miles, 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 |
|
SMOKY
QUARTZ & ORTHOCLASE |
Mineral collecting is centred on the Northern
Arran pluton - the granite of Goat Fell and surrounding
peaks. There is
also an old barite mine, to the north of Brodick and
zeolites have also been recorded on the island. |
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. 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. |
SMOKY
QUARTZ |
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, |
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 island
is also the type locality for the equally 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. |
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. The cave became
immortalized after the German composer, Felix
Mendelssohn, on one of his many trips to Britain. 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. Collecting permission 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. |
FINGAL'S
CAVE Hydrothermal
mineral veins are almost non-existent on the islands. One
exception occurs on the Isle of Islay, |
OUTER HEBRIDES This
extended island group forms a bulwark to the Atlantic
Ocean and has a total population of over 26,000. Unlike the
other major islands off Scotland's west coast, 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 specie,s 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 |
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, but the decision must be weighed against the destruction of the natural beauty of the landscape. It is hoped that other sites may well be uncovered without such disturbance. |
| SHETLAND
& ORKNEY ISLANDS North-east of the Scottish mainland are two island groups. Immediately north of John O'Groats 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 Shetlands, a group of islands with historical Scandanavian connections and currently a major offshore centre for the North Sea oil industry. On the Shetland Islands, 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. Sites 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. |
MAGNETITE - Mainland, Shetland Islands. 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. |
the end
References
UK Journal of Mines & Minerals (UKJMM) - vol. 21; pp 9-27.
"Twenty Years in Minerals: Scotland". (D.I. Green/ J.
G. Todd) (2001).
UK Journal of Mines & Minerals (UKJMM) - vol. 24, p.5,
Mineral News.
© Minerals of Scotland - 2008.