Found digging a pond. The rock was inside Gray Clay 18 feet below grade. The person who gave it to me tried cutting it with a grinder. This left an area that looks like steel.

  • Location: Rensselaerville New York, Goggle Maps
  • Colour: Dark Gold
  • Texture: Rough with Bumps
  • Density: Weight: $3.700\ \mathrm g$, Volume $1000\ \mathrm{ml}$, Density $3.7\ \mathrm{g/cm^3}$
  • Hardness: 7+
  • Luster: Shiny with darker dull in between bumbs.
  • Non-metallic, magnet will not work

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enter image description here Rule in inches

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closed as off-topic by arkaia, Fred, Peter Jansson, trond hansen, Gimelist Jul 19 at 10:46

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    $\begingroup$ "Central New York" covers a lot of territory. Could you give the name of a nearby town? "inside grey clay" sounds like it may have been part of a glacial deposit and that would make it even harder to guess. $\endgroup$ – verisimilidude Jul 15 at 1:49
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    $\begingroup$ What's that incision? Is it from the grinder? $\endgroup$ – Jan Doggen Jul 15 at 7:15
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    $\begingroup$ Math is my worst subject, so bare with me. I used 2 Liters of water, marked the level, then placed the Rock in water, marking the New Water level, that is now at 3 liters, from there i am lost on the math formula $\endgroup$ – GuardianV Jul 15 at 18:44
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    $\begingroup$ 8.16 lb 3700 g 3.700 kg just check again on my postal scale $\endgroup$ – GuardianV Jul 15 at 19:00
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    $\begingroup$ Rule in pic 2 is inches so 6 inches is 15.24 cm long and 10.16 cm high $\endgroup$ – GuardianV Jul 15 at 19:07

This is a marcasite nodule. Straight from wiki: The mineral marcasite, sometimes called white iron pyrite, is iron sulfide (FeS2) with orthorhombic crystal structure. It is physically and crystallographically distinct from pyrite, which is iron sulfide with cubic crystal structure. Marcasite is lighter and more brittle than pyrite. Specimens of marcasite often crumble and break up due to the unstable crystal structure.

On fresh surfaces it is pale yellow to almost white and has a bright metallic luster. It tarnishes to a yellowish or brownish color and gives a black streak. It is a brittle material that cannot be scratched with a knife. The thin, flat, tabular crystals, when joined in groups, are called "cockscombs." And if you Google "Marcasite nodule" images, you'll see many more examples. Nice sample!

  • $\begingroup$ Marcasite properties do not match. Density is biger. Hardness is 6-6,5. webmineral.com/data/Marcasite.shtml#.XS7KNmkhUzQ $\endgroup$ – Leukocyte Jul 17 at 7:14
  • $\begingroup$ see above for new pic, using hammer i chipped a piece off and then ground it up, the chip did brake up easy. $\endgroup$ – GuardianV Jul 17 at 15:09
  • $\begingroup$ It is a pyrite / marcasite nodule which can be found in clays, claystones, and shales. Useful reference: Pyrite Formation in Organic‐rich Clay, Calcitic and Coal‐Forming Environments - onlinelibrary.wiley.com/doi/abs/10.1111/… $\endgroup$ – Gary Kindel Jul 17 at 16:00
  • $\begingroup$ @Gary Kindel. Impurities? As the density providen looks reliable and not an analytical error (1L, to weigth is easy if your weigth machine is no broken), and it is a bit low for both pyrite and marcasite. $\endgroup$ – Leukocyte Jul 17 at 20:49
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    $\begingroup$ @Rokman streak test does show Black, and Hardness i used goggle and looking at a few other samples of other rocks i have and put it at 7 $\endgroup$ – GuardianV Jul 23 at 22:36

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