Mostly sand, sand, sand is suggested in the Oman by the layman...

But: "...The remnants of oceanic crust of the Tethys, a sea belt, which originally stretched from East Asia via South Europe North America are fascinating. Pillow lavas store from basalt, as well as their supply columns filled with solidified melt and magma chambers below a prominent fossil seabed. Even the usually  5-10 km deep border to the upper mantle which is called Moho discontinuity, is today for surface observation accessible..."

acc.pers.com. Dr.Obst

This agate is originated from the volcanic deposits of Oman from the collection Hideharu Yamada. He shows more agates from his collectio on www.lithos-grafics.com.