Microfossil picking

There are many kinds of microfossil collections ranging from conodonts and radiolarians, to foraminifers and even microorganisms such as gastropods. They are all spectacular in their own right but they are all the result of hours picking and sorting under a microscope. The most efficient methods will allow the quickest results.

 My favoured method is with a 2inch (5 cm) square grid numbered from 1 to 120 on photo paper. I have a grid on my computer and print it out when I need to make a new picking platform. The way I make my platforms is with a piece foam board, laminating the grid on top (if you bend up the sides it makes it easier to brush the sample into something). I use thick foam board so I can get a good grip on it, then I can move it around easily. The biggest problem sprinkling out of a vile or envelope is the sample goes everywhere. It's a good idea to use a light coloured desk top so you can see the sample that bounces of the grid, I laminated mine with an off white countertop (good for notes also). I also use a barrier or mobile surround when I sprinkle the sample on my grid. Slap the side of the barrier with a brush or pen to knock off any sample, and it must be made of cardboard to avoid static. The reason that I don't use a tray is light, being able to remove the surround means that I can cover the whole grid with sample, and get complete light coverage with no edge shadow.

When picking the first grid of a sample I start at the top left and go diagonally to the bottom right to see a quick sampling.  Instead of picking a specimen and placing it on a slide right away choose a spot on the grid, I prefer the bottom right corner of the grid. This also works well for the "not sures", instead of  wasting time mulling it over put it at the bottom corner and look at it again at the end of the grid. Another good method for small samples is to pick the full grid than turn it around and re-pick it, angle and lighting is often key to seeing things. 

I work with mostly glass vials, as apposed to envelopes. For an original sample vial and the picked portion vial I use a Wood block with two holes cut into it, and  a paper funnel so I can brush the picked sample right into a vile. Standing in a block the vials can't fall over with the funnel, and the less often the sample is transferred the better. 

The best brushes I have found for picking are watercolor brushes, they seem to hold the water best with the best control.  The best way to load the brush is to dip it and rotate it across a surface, your thumb nail is a good example. I prefer a halogen light source, but keep your brush away or it will dry out and you will have less control of what is stuck on it.

I prefer a simple fixed magnification stereo microscope with no eye cups when I am picking microfossils.  By moving my head around slightly side to side and away from the eyepieces,  I can quickly focus on things that are close to the same size or magnification plane.  For me movement and having the lights on (not in the dark with only microscope illumination), also helps with eye fatigue.

The most frustrating thing for me other than the occasional wildlife charging across the grid, is random hairs and fibers.  Sometimes insects, fibers and the like can be collected in the lab as the samples are drying. Hairs and fibers can be anywhere, especially so if you have pets. Once I have a clean brush I never put it down holding it or put it over an ear, I have found that it always seems to find fibers when I put it down. Change the water often and keep the water container clean and covered when not in use.

As far as the actual picking goes, know as much as you can about what you may find. Sometimes a collection will only be one or two fragments. If you know what the inside of an ostracod, foram or radiolarian looks like it will be that much easer to recognize fragments. Try to have a layer no more than one particle of what you are picking thick on the grid.  Look for a range of fossil colors shapes and sizes, also use your imagination and try to see what your looking for in everything that could be...eventually you will see things without even trying. 

If you have any questions or need more specific information contact me rod@renmanart.com


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