"Mineral grains" refers to tiny particles made of minerals, like rocks or crystals, that can be found in substances such as sand or soil. Full definition
It is found in some minerals, and can be used to trace the source of mineral grains carried long distances by water or wind. (sciencenewsforstudents.org)
The X-ray technique measures an average signal from many tiny mineral grains, providing high resolution and fast data collection. (sciencedaily.com)
This is not liquid water, but water trapped in volcanic glasses or chemically bound in mineral grains inside lunar rocks. (sciencedaily.com)