I need help in indentifying this rock.. The diameter of the rock is 18cm (Approx) and the weight is 9.876 kgs (21.772853 pounds). It feels much heavier in the hand than an ordinary earth rock. enter image description here

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  • $\begingroup$ The colour of the streak is grey/silver and brown.. $\endgroup$ – user8269 May 31 '17 at 13:28
  • $\begingroup$ This rock was found after the ground was dug about 10 mtrs deep. $\endgroup$ – user8269 May 31 '17 at 13:56
  • $\begingroup$ Please follow this guide when asking for rock identification: meta.earthscience.stackexchange.com/a/125/56 $\endgroup$ – arkaia May 31 '17 at 13:57
  • $\begingroup$ Where was this found? A location may help in its identification. $\endgroup$ – Gary Kindel May 31 '17 at 14:57
  • $\begingroup$ This was found in North East India in 1999.. Could this possibly be a coal ball or? $\endgroup$ – user8269 May 31 '17 at 15:04

Based on appearance and density 3000-4000 kg/m3, it might be:

  • Iron sulfide (pyrite and/or marcasite) concretion. It might a have a sweet sulfide smell.

  • Manganese oxide nodule - This would be soft and should be able to scratch with a knife blade.

  • Density is a bit high for basalt, but could be iron rich.

  • Igneous Gabbro/pyroxenite cobble - Density matches.

You may need to break or cut in half with a rock saw to know more.

  • $\begingroup$ The outer layer of it looks like a fusion crust and I had to use a hammer just to get those marks.. $\endgroup$ – user8269 May 31 '17 at 15:35
  • $\begingroup$ And after it was sent to Geological Survey of India, petrology department they used some chemicals to rubbed off the outer layer(black).. $\endgroup$ – user8269 May 31 '17 at 15:38
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    $\begingroup$ You should get an accurate density measure using weight divided volume measured by water displacement. I estimated the volume based on your description but an accurate density would help narrow down the possibilities. $\endgroup$ – Gary Kindel May 31 '17 at 17:06
  • $\begingroup$ I've never heard the word "sweet" together with "sulfide smell" before :) $\endgroup$ – Gimelist Jun 3 '17 at 7:37

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