enter image description here

Is this rock granite? Can anyone help me identifying this rock and describing it?

  • $\begingroup$ Welcome to Earth Science Stack Exchange. Please see our guidelines on rock identification requests and add the necessary information to this post. $\endgroup$ – casey Nov 9 '15 at 2:32
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    $\begingroup$ It looks like exposed aggregate concrete (i.e. man-made) to me. An exact location and some other details, as per @casey's link, will help a lot. (Either way, it's definitely not granite.) $\endgroup$ – kwinkunks Nov 9 '15 at 19:03
  • $\begingroup$ @kwinkunks or a conglomerate. But yea, definitely not a granite. Doesn't even look like an igneous rock $\endgroup$ – Gimelist Mar 8 '16 at 4:21

At first glance it does look a bit like granite, but on closer inspection it clearly isn't. There are at least three components. The dark grey clasts are mostly angular with some partly rounded, and hence are derived fragments of some other rock, possibly siliceous, but could be carbonate. There are smaller pinkish fragments, again possibly siliceous - detach a particle and test its hardness. The whole is cemented together by some whitish mineral whose composition and texture is impossible to determine from the photograph. So to summarize I would say it is a clastic sedimentary rock, or conceivably a volcanic agglomerate - though I doubt it.

Like most rock photographs on stack exchange, there isn't enough detail to give a clear answer. Please also note that rock identification in general is not just by visual inspection. It's a combination of field associations, overall rock texture, macro- and micro- appearance, detailed optical properties, hardness, response to acid, 'streak', density and mineralogical associations.


http://geology.isu.edu/Alamo/rocks/breccia.php The Alamo Breccia is one of the best-preserved impact-generated rock intervals on the Earth's surface. Today it is exposed throughout 25 mountain ranges across southern Nevada and western Utah. The formation of the breccia was triggered by a bolide impact into the Late Devonian seafloor, consisting of limestone. The force of the impact carved through much of the underlying strata, creating limestone rock fragments that were driven outwards and re-deposited as the Alamo Breccia. Tsunami waves generated seconds after impact carried sediment away from the crater (surge) and back into the crater to fill the void (resurge).enter image description here


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