NASA acquired the above hand lens image on February 14, 2016, Sol 1253. Mars Rover Curiosity dumped the sieved sample onto a rock between Namib Dune and High Dune in Bagnold dune field in Gale Crater, Mars. Most of these particles are ooids. Red arrows point to well-preserved spherical ooids. Yellow arrows point to ooids that has been eroded into hemispheres. These ooids are all smaller than 1 mm across.
Highest resolution: https://www.flickr.com/photos/fossil_lin/24947588871/sizes/o/ , which is 400% of source image