Collecting minerals around the world

 Trevor Devon (UK)

At some time, I suppose we have all collected rocks or minerals when we were travelling to new places, mostly as mementos, but nothing quite beats the buzz of collecting specific minerals from classic locations with like-minded colleagues. This type of collecting implies you know something of the geology and mineralogy of the location, what sort of rock to explore (often with a sledgehammer to start with) and what colour and shape the minerals are likely to be found in. Of course, it helps to travel with colleagues who have been there before and can show you what to look for. That is one of the reasons why I joined the Sussex Mineralogy and Lapidary Society (SMLS) a few years ago.

Since 1980, SMLS has conducted trips to many parts of the world, including the USA and Canada, India, Namibia in Africa, and several countries in Europe. Such trips usually attract around a dozen or so participants and are often organised with a bit of tourism so that non-mineralogical spouses can join in. I have been fortunate enough to join recent SMLS trips to Cornwall, Isle of Skye, India, the South of France, the USA, Canada, the Caldbeck Fells in Cumbria, and Bulgaria.

Perhaps I should start with the basic question of why I collect minerals. First of all, I think some of us are born collectors – for example, I collect stamps, books and minerals. Then there is the aesthetic aspect – in my opinion many postage stamp designs are miniature works of art and, likewise, I feel that many mineral crystals can be enjoyed as works of art too – nature’s sculptures. As a scientist (a chemist by training), I also enjoy an activity that uses (and extends through research) my chemistry background. Finally, collecting minerals on trips is a great group activity, in which the other people are intellectually stimulating and fun to be with.

So, what sorts of minerals are collected on these trips? Well of course that very much depends on the locality. In places like Cornwall, Derbyshire and Cumbria, where there has been a tradition of mining (mostly metal ores, fluorite and barite), collecting tends to be from old mine dumps and quarries. Of course, access to quarries is now very limited, because of the owners’ concerns about health and safety issues, and litigation in the event of an accident. Looking over mine dumps (that are generally in the region of 100 years old) is usually productive, but the minerals are generally microscopic (for example, lots of blue-green copper secondaries and brown-black iron minerals) needing a hand lens to spot them. Old quarries vary in yield from microscopic to small hand specimens (for example, fluorite, calcite, barite, quartz and siderite).

Going to more remote areas where there has been volcanic activity in the distant past tends to be more productive for larger specimens (for example, silicate zeolites) and interesting minerals. Both the Isle of Skye and India provide this sort of environment – large areas of basalt, in which a wide variety of alumino-silicate minerals, mostly zeolites, have been created from superheated steam reacting with, and dissolving, the silicate-based basalt. These minerals crystallise out of solution in cavities (vugs) created by the hot steam within the basalt and form often quite spectacular crystal clusters. In Skye, small hand specimens of thomsonite, stilbite, analcime, apophyllite and chabazite can be found by combing the beach on the southwest coast, by breaking open some of the boulders.

This is especially true in some of the remoter beaches (accessible only by scaling 245m cliffs) can yield very fine crystal specimens indeed. The western Maharashtra state of India also boasts vast basalt deposits known as the Deccan Traps. Here, there are many quarries for extracting building stone and roadstone (Fig. 2). The zeolite crystals found here are considered a “nuisance” by the quarry owners, but such is the size and quality of these crystals that Indian mineral dealers make arrangements to collect the best specimens as they are uncovered.

In our trip to India, friendly dealers arranged for us to visit a number of the most famous quarries around Mumbai, Pune and Nasik. In the latter, we were also invited to the Gargati Museum, where we could see the fantastic range and size of minerals that have been collected in the region. Although limited to a few dozen more common mineral varieties, the quality of the collecting was quite outstanding, particularly the size of the crystals. In one quarry, we were present when a new section of the quarry face was blasted out with dynamite. When the dust had cleared, we were able to search for new pockets of minerals that had now been freshly uncovered. It was just amazing to look at crystals that had not been seen since their creation, millions of years ago.

From India, among many other minerals, we were able to bring back impressive hand specimens of apophyllite (especially from the famous Jalgaon Quarry), stilbite and heulandite crystals, as well as beautiful small clusters of the blue-bladed crystals of the vanadium-bearing silicate cavansite from the Wagholi Quarry. In one location, we found two rare (for India) zeolites, levyne and cowlesite in small vesicles (of less than 10mm) in the matrix rock and I had the even rarer good fortune to find a specimen with both these minerals in the same piece of basalt.

The SMLS trip in 2006 to North America took us away from the basaltic minerals of Skye and India to the world’s most prolific zinc mine (Franklin and Sterling Hill, New Jersey), the mineral capital of Canada (Bancroft, Ontario) and the famous Mont St Hilaire quarries in Montreal. All of these locations are stars in the mineral world and are associated with large numbers of different minerals, several of which are ‘first finds’. For example, at Sterling Hill/Franklin, over 340 minerals have been found (10% of all known minerals). Of especial note at Sterling Hill was night time collecting using UV lamps, where the ground lit up in spectacular red (calcite) and green (zinc silicate and willemite) (Fig. 3). We also collected wollastonite (SWUV yellow) and norbergite (SWUV golden yellow).

Entering Bancroft, the road sign proclaims the area “Mineral Capital of Canada” and certainly, in the surrounding countryside, there are many mineral-bearing pegmatites to explore. One of the easiest is found on the side of the road at the Essonville Roadcut, where shiny black blades of fluororichterite can be extracted from the feldspar matrix without much difficulty: I found several attractive little (1cm to 2cm) doubly terminated crystals there. Up at Bear Lake, we dug for the world-renowned apatite crystals (Fig. 4), but only found lots of small pieces (Fig. 5) – it was clearly a place where you need to dig in for several days looking for the mineral-bearing granite pegmatites. Bancroft was famous for its sodalite mines and this blue silicate and the related pinkish hackmanite were easily found on mine dumps (and both show up clearly at night with UV lamps). While in Bancroft, we visited an active rose quartz quarry and a beryl pit, and for a small fee, did some easy collecting of hand specimens.

Our last stop in North America was the Mont St. Hilaire quarries in Quebec, 40km northeast of Montreal, which is a Mecca for micromineral collectors from around the world. Over 350 minerals have been found here, of which 50 have been new minerals. The quarries are now actively worked for roadstone, but the enlightened quarry management allows access to mineral collectors five or six times a year on specific Sundays under the supervision of the local mineralogical society. Such is the popularity of these days that, when we arrived half an hour before the quarry opened, there was already a long queue of cars waiting to enter. Inside the quarry, the sight of the towering side walls added to the majesty of the place.

The geology of the 100myr-old rocks is very complex, as the environment varies across the quarry to include pegmatites, syenites, xenoliths, breccias, hornfels and limestone. Collecting seriously requires some knowledge of the various rock environments in the quarry, as the interesting minerals are microscopic and really require some reference specimens to help with identification. Fortunately, two or three local experts were on hand to tell us about the history of the mineralogical finds there.

I did come across a number of specimens with small crystals present, but these await serious examination with a microscope and reference materials. On this note, it was interesting to observe the Canadians at work – they just collected bucketfuls of small rock specimens from the quarry floor and took them back to their estate cars, returning with fresh buckets. Enquiring of this practice, we were told that the winters were long and cold, and so these specimens would be investigated under the microscopes then to pass the time.

In 2006, our society decided to visit Bulgaria, based upon the recommendations of Warrington Mineral Society members, who had twice visited there. Bulgaria is an active mining country, with famous lead mines in the Rhodope Mountains (notably Madan) in the south. In the north near Sofia, we visited a copper mining pit (Elatzite), a goldmine (Chelopech) and an open iron ore pit (Kremikovtsi). Many small mineral specimens were easily found, including shiny chalcopyrite, sharp clear rhombohedral calcite crystals, black stalactitic spires of goethite, black pyrolusite, grey romanechite and small crystals of green fluorite.

However, no gold was found. In the south of the country, we went down a lead mine (that is a whole story in itself) in Madan, but didn’t find any of the unique spinel law twinned galena crystals that this is so famous for (but, we did buy some from the miners). We also collected wonderfully large manganocalcite epimorphs of both the scalenohedral and rhombohedral forms of calcite. In addition, we collected some igneous minerals (andalusite and garnet in attractively crystalline orthoclase feldspar) from a pegmatite, halfway up a mountain side. And, of course, we did find some zeolites in a basalt deposit (good crystals of analcime, chabazite twins, clinoptilolite and harmatome).

I hope the above accounts give some idea of what mineral collecting can be like when properly organised, especially having some local expertise on hand.