Part One: Sources in Nature -- Harvesting Magnetite Sand in the Wild
First, lets look at the many places in nature where magnetite sand may be found. I continue to seek and test magnetite sands from a wide variety of sources from around the world, and I continue to accrue samples, particularly from across the USA, for testing.
Magnetite Sand in Streams, Creeks, Rivers and Arroyos
Dense dark sands which often include high levels of magnetite sand are commonplace in many streams, creeks, rivers and arroyos (floodwater creekbeds which are dry for much of the year) across the world. Magnetite particles, due to their high mass and high density, end up collecting in the same spots in streams and arroyos (floodwater creekbeds which are dry for much of the year) and in bands (particularly near the high water level) on shores, such as those of oceans, bays and the Great Lakes. Not all dense black sands are magnetite; some dense black sands consist of ilmenite, titanomagnetite (both of which are often useful for our purposes as well, as each contains large amounts of magnetite bound to titanium), monazite, a mineral ore high in thorium, or, if the sand is rather heavy but reddish in color, hematite. The easiest way to find out how much of a black sand is magnetite is to simply run a powerful magnet near it or along the surface of the sand while it sits in a pan or bowl. Only the magnetite (and also titanomagnetite, which is gray to dark gray to dark brown in color and ilmenite, the latter of which exhibits much weaker magnetic properties because it is only paramagnetic rather than ferromagnetic) will be attracted to the magnet, while the hematite, titanohematite, monazite, tiny gemstone crystals (garnet, peridot, ruby, etc.) and any other non-magnetite components will largely be left behind; I write "largely" because it would actually take from two to five passes of magnetic separation -- depending upon the "dirtiness" of the sample -- to really eliminate at least 95% of the non-magnetite particles.
Magnetite sand tends to be more abundant in areas where rock, rocky formations and sands are relatively low in silica and are dark-colored and magnetite tends to be far less plentiful in lighter-colored, silica-rich rocks and sands. If you do not live in a magnetite-rich area, the yield of magnetite sand from creek-bed or riverbed sand may be rather low in return for your efforts. In some extreme cases, in areas where lighter-colored silica-rich rocks and formations (such as marble, limestone or sandstone) predominate, your efforts may perhaps yield only a few grams per hour of magnetite sands of usable grain size, due to the low percentage of magnetite in these creekbeds, riverbeds, sands and soils. I know this from experience: I live in the Appalachian mountain range, and the granite which comprises about 20% of the local rock is about 1% magnetite by weight (in contrast to some other parts of the Appalachians, where there is a higher percentage of granite and a much higher percentage of magnetite), and so the sand in local creekbeds consists at most 0.2% magnetite, which, due to the great density of magnetite sand (about 4 to 5 times denser than lighter sands), translates to less than 0.05% magnetite sand by volume - a very tiny amount! Speaking from long experience garnered here in the mountain creeks in the region of the Appalachian Mountains in eastern U.S. where I live, I can tell you that it can be a rather slow and painful process to attempt to collect this tiny amount of magnetite from local creek sands. Even when I use extremely powerful and large neodymium magnets to try to harvest the magnetite from the sands, yields are very low and it is too painfully slow to accumulate more than one ounce per hour of magnetite sand grains of a usable size!
A Few Notes on Commonly-employed Collection Procedures in This Type of Setting
First, regardless of whether your venue of choice is a creek, river or arroyo, it can pay to first spend some time walking the banks or even wading in the water, to find spots where the dense black sands tend to accumulate due to their great density and weight. Such spots will often be on the outside curve of bends in a river or creek, or where water flow changes direction abruptly, or where high-velocity (aka high energy) water suddenly slows down, such as just downstream from the "bottleneck" formed in a creek or river by rocks, where the water transitions from rapid flow to a very slow and tranquil flow as it hits a much wider part of the waterway. For areas which abound in dark-colored rocks low in silica, you may be able to successfully harvest magnetite black sand in quantity from almost any sand deposits in the bed of the creek, river or arroyo.
In general, when you are harvesting in the wild from waterways or arroyos, you will have a choice of either of the two following methods of collecting magnetite sand:
A Few Notes About Gold, Prospectors and Black Sands
When panning in streams, creeks and rivers, gold prospectors across the Americas always look for black sand, as it, like gold, is very dense, and both tend to settle out of streams and rivers in the same places. Much -- but not all -- of the heavy black sand which gold prospectors collect (and ultimately discard as waste) while panning is magnetite black sand. Gold prospectors often use a variety of tools to help them in separating the dense black sands from gold, and we will be examining some of these tools later in this page, as some of them will be very useful as well for "refining" and purifying magnetite black sand.
While we are on the topic of black sands found in streams frequented by gold prospectors, I have a funny story in that regard for you, as follows:
There is a fair amount of gold as well as magnetite and other black sands to be found in some of the streams and rivers in Maryland and Virginia (and also, to the south, in the Carolinas and nearby states as well) and I have long been aware that many hobby gold prospectors frequent such streams (at least where access is legal), and that many of them have large pails of waste black sand sitting around their homes and garages after having repeatedly screened the material for gold particles, aka "values". So, I joined one of the local online gold forums recently, and started a thread wherein I introduced myself as a research scientist who was not interested at all in gold but rather in acquiring samples of magnetite-rich black sand from this region for testing for a non-gold-related research project (i.e., in order to allow me to test the black sand for magnetite content and trace element content and then assess the suitability of that magnetite for use in MEOW-type devices.) And so I asked in my new forum thread if folks were interested in sending me five to twenty pound bags of their waste/leftover black sand, left over from their gold panning and other separation efforts, and I offered to pay them a bit per pound for the sand and also to pay all their shipping and handling costs.
Well, in short order, several forum members wrote to me off-list via private email and warned me that many gold hobbyists are very paranoid about their waste black sand, because many of them have all kinds of vague notions that there is still lots of gold present in such sands in the form of micron-sized and nano-sized particles, and these forum members warned me that my act of soliciting samples of waste black sand would probably wake up all the paranoid old-timers on the forum, who would then become very suspicious of my offer to purchase small batches of "used" or waste black sand. Sure enuf, exactly what these people predicted happened within one week, and three old-timer hobbyists tried to "confront" me, some on the forum and some via private communications, wherein they essentially stated that they did not believe that I was not interested in gold and rather, they told me that they were "sure" that I had developed some kind of super-high-tech method of extracting micron-sized and nano-sized particles and that I would become rich off their waste black sand. These allegations were followed by assertions that I would never get my hands on their waste black sand for any amount of money.
These allegations were pretty hilarious, as, while it is true that all black sand from gold-bearing areas does indeed contain some gold in the form of micron-sized and nano-sized particles, any really experienced gold prospector or gold-savvy geologist can tell you that the amount of gold present in such "micro" forms in such black sand after gold panning/separation is in the order of one ounce per ten or twenty tons, and that it is largely unrecoverable; that is, it is technically recoverable, but that the methods which would be needed to ensure recovery would employ lots of toxic substances and expensive processes, and the cost of extraction would be at least ten times higher than the value of any gold (or other precious metals) recovered! In any case, after these "allegations" about the veracity of my offer and the purity of my motives were aired, a number of the gold forum members seemed to immediately withdraw from me in fear, and the three or four folks who had already offered, prior to the allegations, to sell me five or ten pounds of waste black sand all withdrew their offers. One man from the forum told me rather threateningly that he would not allow me to get rich on "all the gold" still present (i.e., as micron-sized and nano-sized particles) in the waste black sand leftover from his gold panning/separation efforts, and that rather, he planned to hoard all his waste black sand forever in buckets in his garage. By this time, I was of course, laughing my head off at the level of paranoia and defensiveness spawned by my simple and innocent request! Anyway, this experience led me to quickly conclude that there must be better ways to obtain samples of magnetite-rich black sands for my testing than via the route of asking local gold prospectors!
Incidentally, while my efforts to find black sands via that particular venue in the hobby gold prospecting world did not pan out (sorry for the unintentional pun...!), I eventually befriended a nice man further down the East Coast who runs a commercial tourist-oriented gold panning operation along a gold-bearing creek which is rich in black sands, and he and I worked out a deal wherein he is willing to send me occasional five pound samples of magnetite-rich waste black sands in return for a couple of bucks per pound (for his efforts) plus S/H charges.