a preliminary study of more than 100 deep-sea cores from abyssal plains has revealed two examples of recent muddy sands of the graywacke type which , together with the microcrystalline matrix , form a bimodal-size distribution sands have a well-sorted framework of quartz , feldspar , and rock fragments which , together with the microcrystalline matrix , form a bimodal-size distribution that is also typical of ancient graywackes .
C0037098
sands
C0034387
quartz