Greensand or
Green sand is either a
sand or
sandstone, which has a greenish color. This term is specifically applied to shallow
marine sediment, that contains noticeable quantities of rounded greenish grains. These grains are called
glauconies and consist of a mixture of mixed-layer clay minerals, such as
smectite and
glauconite mica. Greensand is also loosely applied to any glauconitic sediment.