Conglomerate is a sedimentary rock which forms from rounded gravel and boulder sized clasts which are cemented together in a matrix
Chalk is a soft, white, powdery limestone consisting mainly of fossil shells of foraminifers
From Latin conglomeratus, to roll together, i.e. from com together + glomerare to gather into a ball, from glomus (genitive glomeris) a ball
From old English cealc chalk, lime, plaster; pebble, from Greek khalix small pebble, in English transferred to the opaque, white, soft limestone
Coarse Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock