Equipment and photography for micrometeorite hunting
A micrometeorite hunt needs only modest equipment to begin, but good optics and lighting make the difference between seeing a black dot and seeing the barred crystals that prove what it is.
Start with buckets, gloves, a magnet in a plastic bag, kitchen and test sieves, and a stereo microscope that magnifies about 10 to 40 times. To photograph your finds, fix a camera or phone to the microscope, light the particle from several sides, and combine many photos taken at slightly different focus into one sharp image.
Key facts
- Essential
- Gloves, buckets, magnet and freezer bags, sieves, trays, fine brush
- Microscope
- Stereo microscope, about 10–40 times, with good top lighting
- For photography
- Phone or camera adapter, or a microscope camera; focus stacking
- Storage
- Micro boxes or slides with labels; dry, dust-free
Collecting and washing
- Gloves: sturdy waterproof gloves for handling sediment, plus disposable ones for the later stages.
- Buckets and a trowel or scoop: one bucket for raw sediment and one for washing.
- Kitchen sieve or garden riddle: to remove leaves and gravel.
- Strong magnets: a neodymium magnet of a few centimetres, used inside a plastic freezer bag. Keep strong magnets away from phones, bank cards, pacemakers and young children, and never let two snap together on your fingers.
- Shallow trays and dishes: white enamel or plastic trays for washing and drying.
Sieving
Test sieves with stainless-steel mesh, sold for laboratories, soils and model railways, let you split your concentrate into size fractions. Useful sizes are 1 mm, 0.4 mm, 0.2 mm and 0.1 mm. Smaller, inexpensive mesh sets made for sieving gemstones or soil also work well. Clean them between samples by tapping and brushing so that particles do not carry over.
The microscope
A stereo microscope (also called a dissecting microscope) is the workhorse. It has two eyepieces, gives a three-dimensional view and leaves plenty of room beneath the lens to move particles around. Magnifications from about 10 to 40 times are ideal for scanning; 50 to 100 times helps for checking surface details. Zoom models are convenient but not essential.
Lighting matters more than magnification. A ring light or two flexible LED lamps shining from the sides bring out the shine and surface texture of spherules. A dark background helps shiny spheres stand out; a white one helps with dark grains.
A compound microscope, the kind used for slides, shows finer detail but has very little working space and usually lights the sample from below, so it is less useful for scanning opaque grains. A cheap USB digital microscope can be a fun starting point but rarely gives sharp enough images for confident identification.
Handling tiny particles
- A fine paintbrush, slightly damp, picks up a spherule by surface tension.
- A needle in a holder, or a sharpened wooden cocktail stick, can nudge particles into position.
- Double-sided tape or a carbon sticky tab on a glass slide or small stub holds particles for viewing and photography. Carbon tabs are what electron-microscope laboratories use.
- Small labelled boxes, such as micromount boxes or gem jars, keep finds safe. Label every one with the sample location, date and size fraction.
Photographing your finds
Close-up photography of particles a few tenths of a millimetre across is a craft of its own. The simplest start is a phone held to the eyepiece with an adapter. Better results come from a camera mounted on a trinocular microscope, or a camera with a macro lens and a microscope objective on extension tubes.
At high magnification, only a thin slice of the particle is in focus at once. The solution is focus stacking: take a series of photographs, moving the focus a tiny step between each one, then combine them with software into one image that is sharp from front to back. Many hunters take 20 to 100 frames for a single spherule. A steady stand, remote shutter and soft, even light from several directions make a big difference.
Include a scale in every image, such as a calibrated graticule or a photograph of a ruler or 0.1 mm mesh at the same magnification, so that others can judge the size.
Beyond the light microscope
The pictures that reveal a spherule's surface crystals in breathtaking detail are usually taken with a scanning electron microscope, which uses a beam of electrons instead of light and can magnify thousands of times. Most such instruments belong to universities and companies, but some museums, schools and societies run outreach sessions, and it is worth asking a local university earth-science department.
Did you know?
Focus stacking was developed for photographing insects and minerals, and is now standard in micrometeorite photography.
A grain 0.3 mm across photographed so that it fills a phone screen is enlarged roughly 200 to 300 times.
Particles mounted on carbon tabs can go straight into most electron microscopes without being moved again.