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.