Unitedstatesofamerica1 Posted September 17, 2015 Share Posted September 17, 2015 This from Northampton countyPolished it up a bit Quote Link to comment Share on other sites More sharing options...
weaver hillbille Posted September 17, 2015 Share Posted September 17, 2015 (edited) Gabbro is my guess. It's like basalt lava, except it forms underground, like granite,Pennsylvania, right? Homework for you:http://www.dgs.udel.edu/sites/dgs.udel.edu/files/publications/ri59.pdfhttp://mrdata.usgs.gov/geology/state/fips-unit.php?code=f42095 Edited September 17, 2015 by weaver hillbille Quote Link to comment Share on other sites More sharing options...
4meter Posted September 18, 2015 Share Posted September 18, 2015 Not knowing where exactly the sample came from, I would guess it is a "Greenschist", that is, a metamorphic basalt from the precambrian period. The sample looks very similar to "Greenschists" of Virginia's northern Mts.What is the rocks hardness?Here is a link to the Geologic Map of Penns: http://www.dcnr.state.pa.us/topogeo/publications/pgspub/map/index.htmThis can help you pin down the types of rocks found in the area you are collecting in. Quote Link to comment Share on other sites More sharing options...
4meter Posted September 18, 2015 Share Posted September 18, 2015 Gabbro is my guess. It's like basalt lava, except it forms underground, like granite,Pennsylvania, right? Homework for you:http://www.dgs.udel.edu/sites/dgs.udel.edu/files/publications/ri59.pdfhttp://mrdata.usgs.gov/geology/state/fips-unit.php?code=f42095I would lean toward Serpentine due to all the green (olivine?) in it. That is why I asked about the hardness. Serpentines are relatively soft, around 2.5 to 5. Most of the igneous rocks of Penns have been metamorphosed.Gabbros tend to have low (< 30%) olivine (green color mineral) content. This hand sample has a lot of a green colored mineral (70 - 80 %) which would make it a Peridotite, that is, if the green mineral is olivine. A'nt Petrology a hoot. Quote Link to comment Share on other sites More sharing options...
weaver hillbille Posted September 18, 2015 Share Posted September 18, 2015 (edited) I reserve my right to change my answer to Peridotite http://www.geol.umd.edu/~piccoli/100/ch4.htmhttp://www.geol.umd.edu/~piccoli/100/Image8.gif Edited September 18, 2015 by weaver hillbille Quote Link to comment Share on other sites More sharing options...
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