How can you tell if desert sandstone has been subjected to onion skin weathering?

Onion skin weathering - does it break away in dome - like LAYERS as when breaking up an onion? Such type of weatherring is common in sandstones that lack clear bedding structures; it is also a common way that granites weather. This is more geomorphological than geological - the result of continual heating and cooling of the rock.





Sandstone grains are described in terms of angularity - six categories from very angular - angular - subangular - subrounded - rounded - very rounded.





shape or sphericity - 2 categories - poor or good





sorting (how varied the sandstone grain size is) very well sorted, well sorted, moderately sorted or poorly sorted.





(See reference below)|||Yes, especially in the field. The nearly spherical sections are usually easy to see around the rock that is undergoing onion skin exfoliation.


The rock itself shows a tendency to rounding.





If you are handed a rock with onionskin weathering it may not be so obvious. The roundedness is a good clue, especially if it is a rock you know is not normally rounded, and not from a river (which you can not tell just by looking at it). ANother good clue is tapping or smacking it. If the piece flakes off as a small spherical section you know it is onionskin weathering.





Sand grains can be well-rounded, sub-rounded, sub angular and angular. These terms can be described more specifically by adding other details.|||Likely by the appearance (which see in link) where an embedded rock exhibiting layers appears %26#039;sliced%26#039; in half revealing its %26#039;skins%26#039; like an onion.