Elemental Analysis of my mystery rock

[Steve in PA]

I posted pictures of a strange, heavy magnetic rock that set off my metal detector in a plowed field over the weekend.
Meteorite, Basalt, or something else? (treasurenet.com)

Last night I smoothed a small area with my bench grinder and shot it with our Positive Material Identification (PMI) gun at work.


I took four shots with the gun and here are the results. These are the only elements that showed up on all four shots. Six other elements showed up on two of the four shots, but I think the gun picked these as "best fit" in order to get to 100%. I think that it can be reliably stated that his rock is composed of Iron, Manganese, Silicon, Aluminum, plus small amounts of other elements that may require a more accurate instrument to determine.

Element	Shot1	Shot 2	Shot 3	Shot 4	Ave
Iron (Fe)	77.3	72.8	76.7	78	76.2
Manganese (Mn)	9.43	13.05	10.54	7.5	10.13
Silicon (Si)	7	6.97	6.07	7	6.76
Aluminum (Al)	1.44	1.21	1.28	1.13	1.27
Titanium (Ti)	0.71	0.24	0.27	0.54	0.44

 

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[Charlie P. (NY)]

Seems to be a chunk of iron ore, possibly Magnetite or Limonite.

 

[Steve in PA]

Seems to be a chunk of iron ore, possibly Magnetite or Limonite.

You are probably right, although the iron content I measured is a little high for either.

Magnetite is a very common iron oxide (Fe[SUB]3[/SUB]O[SUB]4[/SUB]) mineral that is found in igneous, metamorphic, and sedimentaryrocks. It is the most commonly mined ore of iron. It is also the mineral with the highest iron content (72.4%).