Identifying Unusual Mineral Specimen Found in Farmville, VA

Question
Imgur album: http://imgur.com/a/WnnHr

Found this in Farmville, VA. Any idea of what it is/what it could be the result of? Lots of crystal formation, plus the circular patterns look interesting.

Thanks!
Susannah

Answer
Hi Susannah,

Your specimen appears to be a honeycomb or boxwork lattice rock. These rocks are common in you neighboring State West Virginia. They form in a variety of ways but usually take an extremely long time (several million years)to form as weathering, chemistry, and mountain building interact. They probably have their beginning about 400 million years ago during the initial uplift of the Appalachian Mountains. This was followed by fracturing and mineralization with cycles of dissolution and reoccuring mineral injection.

You did an excellent job in taking these series of pictures. Even with this much detail it is difficult to unambiguously identify the minerals and crystals present in your specimen. Here is a simple test that can be used to shed some light on the composition of your beautiful rock. Use some acid (such as strong vinegar) on a few minerals (a drop or two is plenty) to see if they effervesce or fizz. If they do then the mineral crystals are most likely calcite (CaCO3) which is a very common mineral in boxwork lattice specimens. The rounded knobs of crystals may be the mineral smithsonite (ZnCO3), especially if they have a bluish or greenish tint to them. These might react with acid as well. However, it is impossible to tell for sure which minerals are present without further testing.

Hopefully this helps answer your question somewhat. If your are really interested in a FREE identification of your specimen, including a several page report, you can give the outreach project of our university a try. Details are found here: http://college.earthscienceeducation.net/MIN/MINID.pdf