I found a big stone, oval shaped/dark-gray, with smooth surface, heavy 1.7 X 0.5m. Please help me identify it.

Question

First, I found one piece of the big rock and I found the other piece a few centimeters apart. Given the fact that this stone is very hard, I think it was not broken by humans, but by another geological event (earthquake, landslide, avalanche, etc) There are no other rocks like it in the vicinity. Some people tell me they have seen others two kilometers from this one. When hit with a metallic tool, it emits light sparkles. What does this tell me about the history of this area in Haiti characterized by red soil, mountain. There is a mountain 7 to 10 miles away which looks like an extinct volcano one one side. The ocean is about 12 miles away on the other side.

Please follow the links to see two pictures of the rock. http://www.flickr.com/photos/11063933@N08/2150177848/

The mountain that looks like an extinct volcano is located at Latitude (DMS): 18° 21' 0 N
Longitude (DMS): 72° 55' 0 W and 1100 m above sea level. I do not have the coordinates for the location of the rock but it's 950 meters of elevation. (1 m = 3 ft appr)

Answer 1

its probably a basalt rock,

A Basalt rock is a common gray to black extrusive volcanic rock. It is usually fine-grained due to rapid cooling of lava on the Earth's surface. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Basalt is a very heavy rock. Unweathered basalt is black or gray.

Answer 2

That's really not a lot to go on. I looked up a geologic map of Haiti, and see there's a variety of sedimentary and igneous rocks. Some information about the specific gravity (how much it weights for the volume it displaces) might help identify it, as might the streak (color of a line made on a piece of unglazed ceramic).

I'm not sure about the size you listed either, since you seem to have the measurements as meters, but say you found the rocks centimeters apart.

I don't know why, but your description makes me think of an iron or manganese nodule, which can range in size from almost microscopic to quite large: http://www-geology.ucdavis.edu/~sumner/GeoBioTripPhotos/images/dys12_june15.jpg If it was iron and had been exposed for some time, there might be spots of rust on the exterior, as the one in the photo above has, or it could be gray (http://www.ah.dcr.state.nc.us/qar/conservation/WQar448-000di5T.jpg ), but manganese would stay a black-dark gray: http://ruin.seiiki.com/Manganese%20Nodule0.jpg Either of these could have been formed underground, or in the ocean and if the inside lookas like a series of concentric circles, almost like tree rings (http://www.ngdc.noaa.gov/mgg/image/nodule.gif ) that would support my guess.

The metals would be what makes then spark and gives them weight.

If you could take the rocks (or a even a photo with a good description and location) to a local university with a geology department, they might be able to give you an answer.


ADDITION: That's a good sized rock! Although I can't rule out basalt or other igneous rock completely, that rock looks too smooth on the exterior. Basalt tends to have a "granier" appearance: http://www.daviddarling.info/images/basalt.jpg or be pitted from gas bubbles: http://www.earlham.edu/~littejo/photo/art/basalt2.JPG It could be smooth if this was something that was produced by a lava flow: http://volcanoes.usgs.gov/Imgs/Jpg/Photoglossary/20011005-0039_DAS_large.jpg , but if produced in a flow, there should be a lot more than just the one, there should be a group exposed: http://www.kidscosmos.org/kid-stuff/mars-trip-graphics/weathered-basalt-9-0p.jpg unless your stone travelled a considerable distance. And as the basalt cools on land, it cracks in distinctive hexagonal shapes: http://www.flickr.com/photos/49857054@N00/222979267/ The smoothness and lack of others would make it seem more to me as if what you found was something produced in water, either through tumbling action to make it smooth, or produced as a concretion by building up layers of material removed from the water. I don't know that much about the geologic history to know if it's possible that that area had been underwater at some point, and lifted through geologic action.

There's not enought detail in the two photos for me to make out what the interior of the rock looks like - if it's concentric circles like the concretions or a homogenous composition and texture.

Answer 3

Bit of a long shot this - but could it be the remains of an iron meteorite ??