So phase one is compete on my magnetic dust collection. I set out several versions of the magnetic collectors during the recent prolonged rainfall. I have not yet processed much of the material, but the majority of the magnetic dust appears to be small grains of micaceous minerals: phlogopite, muscovite, biotite - perhaps even vermiculite, plus some iron oxide particles from the shingles themselves.
Nothing clearly extraterrestrial, but the scope that I was using wasn't reaching very high magnification, so I won't be able to tell very much until I get a closer look.
Here are the other patterns of magnets that I tested:
For those of you at home, you can do the same thing. You can find a few links to micrometeorite sampling from the downspout on the interwebs (such as the one linked in the previous episode). I have a few additional suggestions, plus a company that specializes in scanning electron microscopy (SEM) sent me an email relating to one of their promotions.
First off, many sites describe using one large, powerful magnet. This works well, but if you think of the amount of time needed to "sort through" all that water or sediment, an array of smaller magnets will provide much more magnetic surface area to work with. I haven't noticed any loss of "attraction" with the less intense magnetic field of the array as compared to one big magnet. But it does make going through lots of material much easier. Plus, you can stick the magnets to a small sheet of galvanized steel flashing and fit it into the gutter directly. I tried two tests. For most of the arrays, I wrapped the magnets in a plastic Ziploc bag (turned inside out). Small rolls of tape helped hold the bag against the magnets - less air space between the plastic and the roof runoff allows more dust to be attracted to the magnet as opposed to washing away. Then I placed the magnet array/bag setup into the downspout gutter with the open end of the bag facing downhill (so it wouldn't fill with water). When I collected the bag, I just reached in and grabbed the magnet array and pulled the bag right-side in: this trapped the dust and remaining water inside the bag. I'll wash the bags into a clear glass or plastic tray for magnetic processing later.
On one magnet array, I simply wrapped a piece of clear packing tape across the surface (sticky-side down), covering the magnets. I took the whole thing inside and once it had dried, I placed another piece of packing tape onto the dusty surface of the array and smoothed it down. Lifting the tape back up, revealed the magnetic dust stuck to the adhesive. I placed this tape on a sheet of white paper (to see the dust, and to keep new dust from sticking to the tape). I'll use isopropyl alcohol to dissolve the tape adhesive and wash the dust into a collection tray.
Here's a closeup of the dusty tape, stuck to the paper:
The enthusiastic folks at "ASPEX" corporation have an ongoing promotion: "Send in Your Sample," to encourage people to send in samples of materials to observe under a Scanning Electron Microscope (SEM). There's even a YouTube video describing some of the methods they suggest. If you don't have access to an SEM, you might want to check it out. There are other good images of various household items viewed at high magnification as well. They state that the turnaround time is a few weeks, but I've heard some reports that the wait can be longer. It might have to do with the volume of material they have to get through, or it might be the difficulty in processing a particular sample. I asked them about using sticky tape to collect material and they said that should work well. Just be sure to tell them you want the stuff stuck to the tape analyzed. Plus, a piece of sticky tape attached to an index card or sheet of paper easily fits in the mail (as opposed to your cat or something).
Just to be clear, I have no affiliation with ASPEX - I'm not planning on sending them any materials since I have access to an SEM here at my University. Although their scanning electron microscope products do appear interesting and I may enquire into the costs of a unit for our department. I understand I'm giving them some "free" advertising and brand-name recognition for the company (their insistence on my using "scanning electron microscope" to describe their product suggests they want specific recognition for that search term). There is also a chance to have more people see the world of the very small. Since it's free, and I haven't heard of anyone being pressured to buy their own machine, I think it's a fine idea.
I'll try to follow-up with some of my own rooftop results soon. It's finals week here at school, so I've got some grading to do.