What gives sandstone surfaces a melted appearance?

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Offline Streets

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∴I found this 1"x 1" piece of sandstone in my yard in Euless Texas.  To my untrained eye, the surface appears to have been melted.  The layer of melting is a bit less than 1mm thick.  The circular features could be the result of bubbling but that is a guess.  It is not unusual to find this type of rock with indications of lava and fossilized wood and other vegetation in this area.  This example is the only one I have seen with the surface I described.  I would appreciate the opinion of an expert.
« Last Edit: 19/06/2015 19:08:42 by chris »

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Offline Bass

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Re: What gives sandstone surfaces a melted appearance?
« Reply #1 on: 24/06/2015 04:39:31 »
I think you are just looking at varnish from weathering- common in desert environments.
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Offline Streets

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Re: What gives sandstone surfaces a melted appearance?
« Reply #2 on: 25/06/2015 22:07:19 »
Well, if 16 miles west of Dallas is a desert, Why is the humidity a problem?  Thanks for the coulda, shouda, wouda, reply.  I'll wait for a second opinion.

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Offline Bill S

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Re: What gives sandstone surfaces a melted appearance?
« Reply #3 on: 25/06/2015 23:10:19 »
I know very little about US geology, so I'm probably not a good one to comment.  One important thing to be sure of, though, is the real origin of the specimen.  Is it local, or could it have been imported; from a desert area, for example?

If you are sure it is local, then some local geological knowledge would help; for example, are there local examples of igneous intrusions?  could it be contact metamorphism?

http://geology.meetup.com/cities/us/tx/euless/

There seems to be geological interest in the area that might be worth tapping into.