by John Pearce

Microminerals are very small mineral specimens that require some magnification and illumination to appreciate them and see the crystals in detail. Not much magnification is needed, a 10 times or 20 times hand lens could do it, but a stereomicroscope with a magnification of 10 to 60 times would be even better. Small minerals with crystals of 1 to 2mm can barely be seen with the naked eye, but can look wonderful under a microscope (see Fig. 1). Sheer magic!

fig1 boltwooditeThe field of view (FOV) in figure 1 is only 13mm and the crystals are 1-2mm long. The crystals on a micromineral specimen are often
perfect and undamaged. Hand specimens are increasingly difficult to collect in the field, but ‘micros’ are relatively plentiful and are also cheap to purchase.

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It is convenient to mount specimens in plastic boxes, it protects them and keeps them dust free. Some collectors mount specimens on
permanent pedestals in a 1”x1”x1” plastic box (micromounts), while many other collectors simply use blue or white tack to attach specimens (microminerals). 100 micro specimens in 1 inch plastic boxes occupy an area of less than a square foot.

One can acquire a new stereomicroscope from around £80 to £800, depending on the quality of the optics, the range of magnification
and whether there is a manual or zoom magnification system. Many reasonably priced used instruments are available on the secondhand market and on-line auction sites such as ebay. Some microscopes have a means of attaching a camera making it easier to photograph specimens through the microscope.

 

Fig.2 (right) Allanite-Ce crystals to 0.8mm on fluorite
from Ardragh Quarry, Maam Cross,County Galway,
Ireland (A digital combination photograph)

 

As a mineral collector, purchasing a stereomicroscope was the best buy I have ever made. Microscopes are usually fitted with a
light, but some people use various types of external lighting. For example, light of the “right colour” (wavelength) and/or light shone through flexible optical fibres, which does not heat the specimen.

 

Photographing microminerals is very important so everyone can quickly see the unique character and beauty of a specimen.
You can imagine the problems trying to take a photograph of such small 3D minerals and “depth of field” immediately comes to mind. However it is now possible to overcome some of this by taking a series of photographs at predetermined, but slightly different distances and using a computer programme to assemble all the “in focus” areas, thereby putting everything that is required into focus (digital combination photography). Figure 2 illustrates an example of this.

 

You don’t have to choose whether you want to collect microminerals or hand-sized specimens, you can collect both and that is
what most collectors do. However, some minerals only exist as microminerals.
If you want to find out more about microminerals, there is a national British Micromount Society (BMS) with branches based in Sussex, Southwest, Midlands, Norfolk and the Northwest of England The BMS has around 120 members who come from all walks of life and with very widely different levels of expertise. They are united by their enthusiasm and a desire to find out more about microminerals.

The main event each year is a 2 day Symposium held in Leicester in September, attended by around 65 delegates (see Roy
Starkey’s report on the 2015 Symposium on MINDAT at.
ht tp://www.mindat .org/article.php/2266/The+34th+British+Micromount+Symposium
also figures 3,4 and 5).

BMS members, plus some overseas collectors, arrive in Leicester with stereomicroscopes and lots of micromineral swaps.
There is a continuous buzz of activity as members exchange information, purchase or swap microminerals, check the identity of various specimens, discuss entries in the latest BMS Newsletter and compare photographic techniques. There are auctions of hand-sized mineral specimens, a couple of mineral talks, some displays of minerals and photographs and a micromineral competition.
A very enjoyable, informal gathering. If you are interested you would be very welcome.
If you want to find out more. then have a look on the BMS website at http://britishmicromountsociety.homestead.com/ or contact me at
This email address is being protected from spambots. You need JavaScript enabled to view it.


Photo credits: Fig. 1 John Hall; Fig 2
David Green; Figs 3,4 and 5 Roy Starkey.
(My thanks to John Hall for some usefulcomments on the first draft of this paper)
John Pearce

 

 

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