Naked Science Forum

Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: Ladybugster on 09/07/2011 02:17:55

Title: what is this rock?
Post by: Ladybugster on 09/07/2011 02:17:55

I found these on the Lake Superior shoreline. Can anyone tell me what they are called? It's light black with green flecks, and I think they're cool!

Title: what is this rock?
Post by: Bass on 09/07/2011 06:46:13

Looks like plagioclase phenocrysts in a fine-grained (or aphanitic) mafic groundmass- basalt or andesite.  Greenish color in the plagioclase may be due to alteration to chlorite or sericite- or may be from weathering.  There are plenty of mafic rocks in the Lake Superior region.

Title: what is this rock?
Post by: JimBob on 04/08/2011 23:13:40

What he meant to say is this Looks like large crystals of a type of feldspar in a fine grained volcanic rock formed from the same material that forms the floors of the ocean. Since the rock came from the Lake Superior area it is VERY old.

Title: what is this rock?
Post by: Saille on 09/10/2011 00:44:27

Quote from: JimBob on 04/08/2011 23:13:40

What he meant to say is this Looks like large crystals of a type of feldspar in a fine grained volcanic rock formed from the same material that forms the floors of the ocean. Since the rock came from the Lake Superior area it is VERY old.

I am glad there are translators on this forum. ;-)

Title: Re: what is this rock?
Post by: macjonny on 10/02/2012 10:36:50

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fclasticdetritus.files.wordpress.com%2F2010%2F02%2Frock_21.jpg&hash=fd64bc0edd8a62968227592fa1c769f8)

Title: Re: what is this rock?
Post by: CliffordK on 10/02/2012 11:11:27

That last rock seems to be part of a geopuzzle from another site.

http://clasticdetritus.com/2010/02/04/geopuzzle-what-is-this-rock/
http://clasticdetritus.com/page/9/

And, of course, an unrelated link from the person posting it.