I found this half submerged in Skegness beach, UK, on the sea front.

Color: Black
Lustre: Dull matte
Texture: Very grainy
Weight: 921 grams. Seems heavy
Size: 6 x 4 inches or 120 x 150mm MOH scale: 2.5 scratched with fingernail

I think I can rule out coal: it's too heavy and doesn't leave any black marks. It seems very grainy where coal is flat and grainless.

enter image description hereenter image description hereenter image description hereenter image description hereenter image description here


closed as off-topic by Leukocyte, Peter Jansson, Erik, trond hansen, arkaia Sep 3 at 18:00

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions about rock identification requests are off-topic. For more information, see the announcement on meta." – Leukocyte, Peter Jansson, Erik, trond hansen, arkaia
If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ Is this the same rock as your earlier question? Please merge the 2 questions together if so. $\endgroup$ – mkennedy May 31 at 22:29
  • $\begingroup$ How ? Someone said i needed more info so i re did it how do i merge $\endgroup$ – Chris May 31 at 22:46
  • $\begingroup$ It might be difficult to id, coal unlikely because it is too heavy, hematite is too hard, basalt is too hard, shale too hard (typically). Best guess and it is a guess is that some shales become soft with exposure to water? A better picture from different angles might help. When photographing a dark mineral a darker background might lead to a better exposure, or slight overexpose the shot. Also some description about the grainyness and whether cleavage planes are present might help. $\endgroup$ – Friddy May 31 at 23:21
  • $\begingroup$ Other than the weight aspect it kind of looks like coal, using the previous question. When assessing hardness how would you describe the scratching with your fingernail, did your fingernail break off loose bits or did it scratch deeply exposing fresh material. $\endgroup$ – Friddy May 31 at 23:27
  • $\begingroup$ I think you can rule out coal its definitly to heavy and doesnt leave any black marks it just doesnt seem like coal to me and seems very grainy where coal is flat and grainless $\endgroup$ – Chris Jun 1 at 10:10

It looks like a fine-grained basalt possibly softened by surface salt intrusion. The other option, and the one I'm leaning towards is that is isn't a rock at all but a piece of weathered blacktop, it looks quite similar to pieces I've seen in the river near my home.

Post break images: Definitely an altered vesicular basalt the vesicles appear to have undergone secondary mineralisation which shows up as the white spheroids in the broken fragments, the lowered hardness is due to salt weathering of the exposed surface material.

  • $\begingroup$ Definitly not blacktop is there a way i can test it $\endgroup$ – Chris Jun 2 at 18:27
  • 1
    $\begingroup$ @Chris Heat it up with a flame, if it softens, or starts smoking, it's some sort of petroleum product. $\endgroup$ – Ash Jun 2 at 18:30
  • $\begingroup$ Ok heated it up with a lighter and didnt do anything, also as it was on the beach and my personal opinion it looks natural not man made $\endgroup$ – Chris Jun 2 at 18:41
  • $\begingroup$ Could it be volcanic ? $\endgroup$ – Chris Jun 2 at 18:41
  • $\begingroup$ I just added two pictures and i hit it with a hammer and it seems to crumble into black sand ??? $\endgroup$ – Chris Jun 2 at 18:44

It is black volcanic sand that has formed into a small boulder.


Not the answer you're looking for? Browse other questions tagged or ask your own question.