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NEWSLETTER No 67 extracts

Below are the articles from Newsletter No67 published July 2004:-

ALPINE CLEFTS IN MID-WALES
Steve Rust

It may be hard to believe but, yes, there are Alpine type clefts in the siltstone/mudstone/ sandstones of the mid-Wales "orefield". Alright, not on the scale of those in the Alpine mounting chain!

 

In Wales Alpine mineralisation is more associated with the area around Prenteg - brookite etc. In fact the mid-Wales cleft variety seldom reaches more than 2cms by 1-2mm wide, although the process for their formation is probably similar.

In mid-Wales the clefts are found in the rock clast breccias in the fault veins which are a conspicuous feature of the mineralised fault systems in the area. The alpine cleft minerals predate the main sulphide influx, but are still part of the overall mineralisation.

 

Fault veins in mid-Wales are thought to have formed by the build up of pressure, followed by a rapid pressure release rupturing the surrounding rock along lines of weakness. The resulting fragments of rock were encased in quartz and, or, ferrodolomite. In rare instances, small rock fragments usually to no more than 2cms, were parted along bedding planes but not completely filled. The parted surfaces of the clasts are coated by a thin druse of quartz or, occasionally, muscovite. Very rare accessory minerals within this assemblage are albite, apatite, chlorite, and rutile in euhedral crystals. Although a number of locations have been looked at in mid-Wales for this type of mineralisation, only four have so far come to light. (There are many more to look at yet.)

 

The author believes that the accessory minerals are more than likely to have been "sweated" out of the country rock. Studies of the petrology have confirmed the minerals found in the clefts are a constituent part of the mudstones etc which have undergone low-grade chlorite green schist metamorphism. One perplexing anomaly is the occurrence of monazite nodules in restricted horizons in the mudstones. But monazite has not been re-deposited within the cleft mineral assemblage in the specimens so far collected. This may be due to a number of factors.

a). pH etc not correct for monazite to reform in the clefts.

b). Monazite was remobilised, but was "washed" out of the hydraulic fault system before it had a chance to form.

c). Monazite may have been destroyed by the later acid sulphide influx, but why then were the other cleft minerals not dissolved?

d). Occurrences so far collected from were not associated with the location of monazite nodules with in the mudstones etc.

e). Crystals may have been overlooked.

As this is an on-going study more occurrences will come to light, these are the ones so far recorded.

The alpine cleft type mineralisation was first noted by the author in the mid 1980's at the Bryn yr Afr mine.

Bryn yr Afr Mine. (SN745879). Albite, apatite, muscovite, quartz, rutile.

Esgair Hir Mine. (SN734913). Chlorite, muscovite, quartz.

Darran Mine. (SN675828). Albite, muscovite, quartz, rutile.

Castell Mine. (SN775813). Albite, apatite, muscovite, quartz, rutile. The examples from the Castell mine are the most recent find (2004). Also specimens from this mine are by far the most abundant occurrence of euhedral apatite crystals.

Albite. Forms tabular mostly striated crystals to rarely 1mm, commonly twinned.

Apatite. Occurs as colourless to white tabular hexagonal crystals to no more than 0.7mm in diameter. Some crystals have a distinct triangular aspect to them - probably the result of rapid growth in only three directions.

Chlorite. So far only noted as green platy crystal rosettes to 0.4mm, from Esgair Hir mine.

Muscovite. Relatively common as a drusy coating of thin colourless to milky petal-like crystals to no more than 0.3mm in diameter on cleft surfaces.

Quartz. By far the most abundant mineral in the clefts, usually as the only mineral present. Pleasing as single scattered double terminated colourless crystals to 2mm. Sometimes as broad tabular forms, very rarely as tabular fadens.

Rutile. A rare accessory mineral in the cleft assemblage, as finely acicular pale brown crystals to 0.6mm long.

 

 

 

GARRAS MINE NEAR TRURO
Chris Jewson

Anyone having specimens of pyromorphite from Garras Mine near Truro should check them out under a microscope to see if they have any wulfenite present. Most specimens in collections will be hand size and so may not have been checked checked under a microscope.

It is not material that is not widely available but keen collectors of Cornish specimens may have acquired some. I recently bought a piece and was delighted to find wulfenite present, so I got a real bonus and did not feel so bad having paid what I did for it!

It may be worth mentioning that the mine closed in 1820 and ALL the dumps have long since been cleared away so do not bother even thinking of wasting your time going there in the hope of finding a stray piece - there isn't any!

 

 

 

MICRO PANS
David Roe

I am beginning to feel an enthusiasm for creating a schism in the massed ranks of the BMS. Nothing less than the birth of the British Micro-Panning Society! I can see little to stand in the way to world domination - in less than six months the membership of BMPS (it trips off the tongue) has doubled. I therefore confidently expect Bill Mason and myself to be overwhelmed at the Symposium by those who are jaded by digital cameras and wish to return to a simpler life. For what can bring us closer to our elemental roots than standing knee deep in a rustic stream surrounded by curious heifers and a haze of midges?

I confess to be a failed gold panner - have gold pan, prime locations and necessary hand eye co-ordination - but a depressing inability to predict where the battered gold nugget, swept by life's torrents on its path to the sea, will end up. As a result that magic moment in panning, when the contents of the pan go from off white to black as the last of the quartz is riffled away, rarely results in a flash of gold. However in Devon and Cornwall it often provide a chocolate brown heavy fraction. At the end of one evening's work on the river Dart I tried to cheer myself up by examining my nugget (aka flake, pinhead, microscopic fleck) at X30 magnification and became fascinated by what the microscope revealed.

Eventually curiosity got the better of me and I methodically analysed the heavy fraction separating out the gold nuggets (see alternative appellations above), from the inevitable lead shot, welding splatter (I believe that to be the technical term and it originates from a garage located upstream)) and magnetite. Much of what remained was obviously honey brown to treacle black cassiterite but with a surprisingly high level of lurid red fragments that looked suspiciously like garnet or perhaps even zircon. Zircon has a special place in my memory as my first introduction to panning had been in Mid France in the le Puy region where 30 years ago it was easy to pan out rather handsome blood red crystals of zircon measuring 2-5 mm from the stream at Esplay near St Georges d'Auric.

So did the River Dart yield garnet, zircon or cassiterite - chemistry was needed. Dilute hydrochloric acid followed by zinc powder produces a metallic grey coating of tin on the cassiterite grains -which can be dissolved off by the addition of more acid. To my surprise the zinc test showed that most of the blood red material was cassiterite with only a few dark coloured dodecahedral garnets left uncoated.

The Micro Panning craze then moved to Cornwall and the historic site at Manaccan - on the Lizard. This was where titanium had first been discovered as a heavy fraction in 1802 as menaccanite (later renamed ilmenite). This is a much more complicated mixture - dominated by magnetite, then ilmenite (not a pretty mineral) then cassiterite and finally a few garnets and just a whiff of gold. I am still working on how to separate the ilmenite from the cassiterite - Oh for a method of variable density separation for density 4 and 8.

Back in Devon one location in the vicinity of Peter Tavy has given Bill Mason and myself a lot of fun this summer. Battling through barbed wire and gorse reminiscent of the Somme we have been following a stream that seems to be yielding something very different. Not a sniff of gold, a little tin but also a fair quantity of tiny garnet like crystals. Most of these are off-white to grey and less than a millimetre across but occasionally there are water clear crystals with a diamond sparkle. We have convinced ourselves that we have hit zirconia pay dirt - any one like to assist us by analysing a sub millimetre crystal - life membership of the BMPS is assured.

 

 

 

ZEOLITE COLLECTING ON THE ISLE OF SKYE
Ronnie van Dommelen

This past May, my wife Jennifer and I took a trip to Scotland. While on the trip I received an email from the editor requestin g a trip report. I was worried that there would be nothing to report, but as it turns out I have some good news.

We had set aside the first two weeks in May for our vacation to visit friends and tour Scotland, in part with the company of our friends.

Although May was the only time we had available, it turns out that this is an excellent time to visit the area. It is historically one of the driest months - important in an area that is renowned for wet weather. The temperatures are good at this time of year (10-20ºC) and yet it is e arly enough in the year that pesky midges have not yet emerged. It is also early enough that most tourists have not yet emerged. The timing was absolutely perfect.

With the time and place set, we began roughly planning what we would see on the trip and I had to select a place to collect. I would be able to collect one day at most and wanted to make the most of it. The website 'Minerals of Scotland' provided descriptions, directions, and pictures of many localities from which to select. I decided against classic areas like the Leadhills and Strontian for several reason s. First, it might be very difficult to find specimens in these well collected areas. Second , they are south of where we wanted to concentrate our visit, which was in the highlands. Thirdly, it might prove difficult to identify many of the minerals collected. The obvious choice then became the Isle of Skye. Being a zeolite collector, this is one of the great and classic collecting localities. Being along the coast, there would be renewal of rock due to erosion, increasing the chance of finding material. Finally, I would have at least a fighting chance at identification of most of the minerals.

Selecting a spot on Skye was also a challenge, but I decided upon Moonen Bay. The description on the website sounded favourable and it offered several zeolites that we don't find at home in Nova Scotia such as levyne, garronite, and erionite (see Table 1 for a complete list). Moonen Bay is located near the northwestern tip of the island with huge cliffs of basalt dominating the landscape.

Skye is about 60 km in length and lies just off the coast of Scotland. Recently a bridge was built to connect it to the mainland . The bridge is the source of great local debate . They feel that it takes away from the mystical feel of Skye. They also don't like the tolls (this was a privately built bridge) when most similar bridges in Scotland are free . The middle of Skye is dominated by the red and black Cuillin Hills comprised of granite and gabro, the colour of which gives them their names. The hills rise to about 1000 meters but are very climbable with fantastic views and some snow at the top. South of the Cuillins, sandstones and gneiss are found but, to the north, lies the revered basalt.

The friends that we were visiting joined us on this part of the trip. One of the friends is a fledgling mineral collector and was also excited about a chance to collect. We were only spending two and a half days on Skye and I knew that the chance of good weather on both was slim. As it turned out we had excellent weather - sun the first day and cloud the second. Both days were warm and dry.

Collecting took place on the first day and we headed out from the main town of Portree towards Neist Point. The secondary roads in Scotland are quite narrow and especially so in Skye. Many of the roads are a shared single lane with occasional short bulges in the width to provide for passing of oncoming traffic. The roads also snake around and up and down over the hills.

Figure 1: Moonen Bay from the parking lot. Waterstein Head rises dramatically above the bay . Collecting took place at Camas nan Sidhean, the beach along the closer inlet Luckily, one of our friends was a native Brit familiar with the roads - it was very much like a roller coaster. At the end of the road is Neist Point with its lighthouse, sometimes seen on postcards in the local stores. There was a small parking lot at the end and we were surprised to see several other tourists there. Moonen Bay lies to the south and is quite dramatic as shown in Figure 1. There were huge cliffs at the edge of the sea and, in the foreground, green fields trailing down to their base. The field was a grazing area for the many sheep that curiously watched us pass and, well, sheepishly ran away as we came close.

Tides are a factor in the area but we had planned to start as the tides were falling to ensure no problems. When we arrived it became clear that the area of Moonen Bay described on the website was a farther walk than I had expected . Nonetheless, the closer beach of Camas nan Sidhean, still part o f the larger Moonen Bay, had lots of visible rock as did the scree slope from the cliff, so we headed off. The trails that the sheep had made on the hillside came in handy as we made our way down to the beach . As we got close, I began to notice areas of basalt sticking through the grass. They were quite crumbly, but very mineralized. The beach was even more interesting. There was a low cliff along the back side of the beach that was about 4 meters high. It was composed entirely of boulders, up to a couple meters across with sand and soil packed in between. Perhaps this was the remains of a huge debris pile left over from the last ice age. Whatever the origin, the sea plucked boulders from the low cliff and dropped them onto the beach making for a mineral collecting buffet! Figure 2: On the boulder strewn beach looking back towards Neist Point. A few boulders can be seen on the right side of Figure 2 (the rock in the distance does not contain zeolites). Some of the boulders were barren but a great many were highly mineralized. Collecting in boulders rather than from the side of a cliff makes life a lot easier because the boulders are easily broken down into smaller pieces. The Minerals of Scotland website says that this is only a recently discovered collecting area , which is very surprising given the amount of minerals.

By far the two most common minerals that we encountered from this area were thomsonite and chabazite. The thomsonite was white to pale yellowish in colour and formed drusy coatings lining many of the pockets. The chabazite formed excellent colourless to white, lustrous and sharp rhombs. Analcime was also common as druses of white lustrous crystals. We also found a few specimens of a delicate white radiating zeolite. Based on its visual appearance and the list of reported minerals, it is likely mesolite. One of the delicate mesolites had smaller crystals of probably calcite that were speared through near the tips of the mesolite, and was visually quite appealing.

Although we didn't find any of the rarer zeolites, there was certainly a lot of micromineral material available.

Some larger specimens were found too. Near the end of the day I found what was probably a 3 cm chabazite crystal on the bottom of a boulder, but did not have the time or heavy enough tools to collect it. A spray of mesolite about 4-5 cm long was found when opening up one boulder, but unfortunately the crack went right through the specimen. Finally, a calcite of about the same size was found on a boulder hanging dangerously from the top of the cliff. So, while we didn't have much luck collecting them, larger specimens are certainly available for those who are interested in such things.

It didn't take long to gather as much material as I would be able to take back on the plane without leaving my clothes behind, so we headed off to do some other sightseeing. I didn't get a chance to check the scree slope at the base of Waterstein Head, but this might also be fruitful as it would give a sampling of all the different layers in the cliff.

In all, the trip was fantastic and highly recommended . Skye was definitely a highlight, and I'm sure a whole trip could be devoted to collecting this area. The feeling I get is that it is not heavily collected and with some time and effort, many good specimens could be found

 

 

 

Table 1: Reported Minerals

Zeolites

Other

analcime, chabazite, cowlesite, erionite, garronite, heulandite, laumontite, levyne, mesolite, phillipsite, stellerite, stilbite, thomsonite

apophyllite, calcite, copper, gypsum, gyrolite, pyrite,

 References "Mindat.org - The Mineral Database", Jolyon Ralph (editor), www.mindat.org "Minerals of Scotland", H. Currie, www.curriehj.freeserve.co.uk

The above article was first published in the May/August 2004 issue of Micronews, the Newsletter of the Canadian Micro Mineral Association. It is reproduced here with the kind permission of the author, Ronnie van Dommelen. Ronnie says "By the way, if any of your members are, like myself, zeolite collectors of all sizes, and are interested in zeolites from the Bay of Fundy, they might like to check out my website: http://is2.dal.ca/~dommelen/mainrock.html and a heavily updated, under-construction version temporarily at: http://www.optics.ee.dal.ca/website/test.html.

I have lots of extra material and could trade or sell excellent zeolites of all sizes (though generally larger than micro)."

 

 

 

TANTALISINGLY CLOSE TO THE BAVENO QUARRIES
Max Wirth

I am getting too old to travel, but in the Spring (2004) the Lakeland Horticultural Society (of which I have been a reluctant member for many years), advertised a tour to Lake Maggiore (not the major lake, but fed by the river Maggia!). On the way to our hotel in Cánero, we saw the vast quarries above Baveno, the Agrano, the Montecatini. The object of the tour was to see the camelia and magnolia in full blossom, but my secondary objective was to see whether I could enter the Baveno quarry (of baveno twin fame).

I regret to say that, although I saw millions of blooming (in the true sense) shrubs, I never managed to get to the quarries. They were only open to visitors at the weekend (all day guided tour £16). The only specimen I found was on a market stall on the other side of the lake, amongst the clothes, leather goods and tourist trash. At least it was in pink granite and carried barite with minute fluorite and galena crystals. It took some hard bargaining to bring it down to 20% of the asking price. This is of course foreign stuff and will not grace our collection.

On the last Sunday we actually stopped for a couple of hours in Baveno itself and I thought I would find a mineral dealer. With my very limited Italian I discovered where there was such a shop and eventually found it - shut and steel shuttered.

Almost every day, sitting in our coach, we passed a little sign on the roadside in Ghiffa, saying 'Cambio minerali', but it was impossible to stop. Back at our excellent hotel, Mr Galllinotto, one of the owners, promised to find the address of this little dealer; it was Mori Osvaldo in Ghiffa.

Back home, I wrote to him sending him a few bits of Shap material and asked for similar specimens from Baveno. He replied in English (courtesy of what he called 'a girl', presumably his daughter, as translater). He sent me two bits of bavenite, some pistacite (epidote!) on smoky quartz which included a small orthoclase (baveno!) and a specimen labelled babingtonite which is perhaps the scandiobabingtonite (TL Baveno). I returned the compliment with some alstonite etc., promising a further exchange in due course.

All in all, I can not complain and I certainly enjoyed myself.

 

 

 

LITTLEHAM COVE
Greg Towning

CONCRETIONS CONTAINING URANIUM, COPPER, ARSENIC, COBALT AND VANADIUM MINERALS AT LITTLEHAM COVE, DEVON.

There is an unusual occurrence of secondary uranium, copper, arsenic, and vanadian minerals in the Permian mudstone cliffs at Littleham cove near Buddleigh Salterton/ Exmouth, East Devon. They generally appear in rounded concretions, and are found immediately east of Straight point, almost at Buddleigh Salterton.

Grid reference SY040802 - SY053813. Access is by one of two ways. The first is by a footpath down the point, near the first grid reference above. The path is steep and then one has to walk across wet rocks to get to the beach - access is at low tide only. The other way is the 2.5km plod over quartzite pebbles and through the nudist bathers (yes even in winter!) from Budleigh Salterton.

 

 

 

The concretions are easily found both in the mudstone slump edges, littering the beach and in fallen blocks, particularly after falls. It should be pointed out that the cliffs are unstable in places, the slumps are very wet and collecting from the cliffs and climbing the slumps is potentially dangerous.

 

 

 

DESCRIPTION

The concretions are rounded, often resembling balls. They vary in size from near pea size to the size of a small football. The largest I have found measures 25cm in diameter, although the average is around 5-10cm. Some concretions have a winged appearance with a flat disc around the edge. Where they show in the brown mudstone matrix, there is frequently a dark green halo around the concretion.

The concretions, when carefully broken open, often have round alternating black and grey zones; they generally have a small round black core. The surfaces (both the inner and outer) are frequently covered in yellow, green, blue and pink crusts. The concretions are radioactive, though the majority are very weak. There is a fair minority however which are 'hot` and should be checked with a Geiger counter if you intend to keep them. Many of the concretions are solid and are of not much interest to the micro collector, though every now and again one can find them with richly mineralised vughs or with a metallic core.

 

 

 

THE MINERALS

The location has a complex mineral suite and all of my specimens have been identified visually only. It is probable that some have been misidentified. I have detailed problems with identification later in this report.

The location has an impressive list of minerals; some of them very rare, which have been recorded. Those for which I am fairly confident of the identification are listed below. The uranium and uranium secondary minerals are coffinite and metatyuyamunite (and tyuyamunite). The coffinite occurs in the black zones of the concretions and the metatyuyamunite as yellow crusts and micro-crystals, including micro cubic epimorphs crusted with metatyuyamunite crystals. I have found a micro, which appears to be zeunerite (this mineral has not been recorded here, to my knowledge) and I have also found an unidentified crystalline, soluble orange mineral, be wary about washing specimens.

There is a vanadium mica called roscoelite this appears as silvery sheaves of mica within the concretions. There are many different green crusts/areas, some of these change from the yellow metatyuyamunite and I wondered if this could be volborthite. Of the arsenates erythrite- another common mineral found - appears as pale pink crusts on the surfaces (outer and inner) of the concretions. I have found some lovely micros of rich pink erythrite spherules. Lavendulan forms as blue micro crusts and spherules on inner surfaces. I have several micro-specimens, which appear to be sulphur arsenides, grey/silver in colour showing complex and striated forms (most very small) including possible arsenopyrite stellates or trillings. With the copper minerals, crusts of malachite are common. I have found micros of chalcocite, which are fairly common and in a variety of forms, some of which are lovely. I have at least one micro specimen each of covellite and chalcopyrite.

I have also found, again all in micros, a variety of pretty calcite crystals, atacamite or similar, aragonite and dendretic pyrolusite.

There are also natives and minerals related to silver. The finding of native copper disks or plates has been well documented, mostly found in the 70's; these are thin (4mm) discs up to 160mm x 90mm. A number of the plates assayed at over 99% copper, with some minor cuprite and malachite. Native silver has been recorded with the disks as well. I have found small micros of native copper and one very small specimen, which I believe is native silver, with the dendrites showing fairly clearly. I believe I may have also found a very small number of silver related specimens including chlorargyrite. These require confirmation.

Many of the micros I have only found in small numbers, most of these are tiny in size and unusual. Identifying many of these is proving very difficult. Partly due to the reasons mentioned above, though, no doubt, also because of the relatively few collectors who collect there. The general mineralogy is moderately well documented but with really very little on micro specimens, many of which are undoubtedly rare. With such an unusual mineral suite, there is surely a high chance of finding new and unrecorded minerals for the location.

 

 

 

THE BMS REFERENCE COLLECTION
Max Wirth.

Since the editor was desperate for some copy, I decided to include a few comments on recent specimens as well as a few moans about their scarcity (I would not want Mike to be the only one to complain). I do not know what has happened to collectors, perhaps they are too preoccupied with photographing their own specimens and do not have the time to go out collecting, let alone sparing the time to fill in record cards and entering bits for the collection. This is all that has been received this past year:

2365 TITANITE/ALBITE Loanhead quarry Beith Scotland Bottomley,J.
2366 HEMATITE/ ANALCITE Loanhead quarry Beith Scotland Bottomley,J.
2367 WROEWOLFEITE Frongoch 24 fathom Dyfed Wales Hay,P.
2368 GOLD Gold Mines River Avoca Ireland Hay,P.
2369 MARCASITE Samphire Hoe Dover Kent Hay P.
2370 HYDROZINCITE Callowhill quarry Pontesbury Shropshire Hay P.
2371 CALCITE Cuckmere Haven Seaford East Sussex Hall J.
2372 BABINGTONITE Ben Bhreac Tongue Sutherland Scotland Meikle K.

Our reference collection now has 2372 entries (most of them worth keeping!). now:

2300 COPPER Cronebane mine Co.Wicklow Ireland Hay, P.
I have replaced some redundant items with recent specimens. These are 2301 CADMIUM SULPHIDE Whatley q. Frome Somerset, Hay, P.
2302 ATACAMITE Dooneen mine Allihies Ireland Hay, P.
2303 TALC Corrycharmaig Killin Scotland Wirth, M.
2304 THAUMASITE Edgcumbe Park Crowthorne Berks. Betterton, J.
2355 SCHORL Hexworthy Dartmoor Devon Blake D.
2356 SMITHSONITE Cavendish Mill Stoney Middleton Derbyshire Braithwaite, P.
2357 SCHORL Ruddy Cleave Br. Dartmoor Devon Blake D.
2358 TITANITE Shap granite quarry Shap Cumbria Wirth, M.
2359 BAZHENOVITE West Runton beach Norfolk Smith, P.

Of course the full listing (as well as record slips!) is always available as an Excel table from the curator. I have also tried to include additions in our website.

 

 

 

WEB MATTERS

WEST MARY ANN MINE - WEB SITE

Please note that there is now a web-site for the above mine at www.minecaptain.plus.com. The web-site contains sections on the history and re-opening of the mine, photographs of the mine and the minerals as well as a section devoted to the Anthony Aldworth collection.

 

 

 

UNITED KINGDOM GEOLOGICAL EQUIPMENT LTD

A new website www.ukfossils.co.uk is operated by the above company. The site offers "comprehensive geological guides for over 120 locations, thousands of photographs, events and discussions". Of course, they also sell from their range of "4,500 Earth Science items" through the web site.

 

Contributions for the Newsletter should be sent to: David Roe,  E-mail Address(es): david@d-roe.freeserve.co.uk


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