What are these rocks? We are importing dirt from local pool companies digging in the area. We live denton, tx (north texas). One company dumped about 4 loads of very red sandy loamy dirt and 3 loads of fine brown sand with some unusual shapes rocks.

I was putting the sand in my garden bed because it's mostly clay and I read that plants would do better with more of a loam. The texture is hard and doesnt scratch off with fingernail. I'll try a knife and see. Different shapes, some are flat, varying sizes.

I suspect these are sandstone, they just are oddly formed. enter image description here

  • $\begingroup$ Welcome to the site Eveman. Please, if possible, leave us a picture with a fresh cut of the rock. It would also be valuable if you can do it using a magnifying glass. $\endgroup$ – user12525 Apr 7 '19 at 9:31

Your rock looks like coarse grain sandstone with ripple marks, but a description of the minerals could clarify if it is a volcanic sandstone or, conversely, it is a quartz sandstone not related with volcanism.

To determine the origin of the sandstone grains you should make a fresh-cut of the rock and, if possible, make a picture too of what a magnifying glass shows.

It probably comes from Woodbine Formation at Denton Country, Texas, USA. That formation has sandstones (both quartz and volcanic ones) from coastal environments, as USGS describes it, where hydrodynamics could have developed the ripple marks, that are little dunes the current form on sands or muds.

"Woodbine Formation: NE Texas. Texarkana Sheet (1966) Woodbine Formation--various interlensing sequence of nonmarine, brackish-water, and marine beds of sand, clay, sandstone, and shale 350-600 ft thick. Woodbine fossils include ammonites, gastropods, pelecypods, brachiopods, and foraminifers. Contains volcanic sand and tuff, coarse grained, crossbedded, dk green and olive green; fossil plants and a few marine megafossils; thickness 500 ft, thins eastward."

Source: Geology of Denton Country, Texas. United States Geological Survey

That formation is digged by pool companies as shown in this maps:

enter image description here enter image description here Source: shaleexperts.com


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