mineral aggregate
concretion
hard, compact mass of matter formed by the precipitation of mineral cement within the spaces between particles
nodule
knot, mass, or lump of a mineral or mineral aggregate with a contrasting composition
saussurite
plagioclase that has been pseudomorphously altered to zoisite, scapolite, albite, epidote and other minerals
druse
incrustation of small crystals on the surface of a rock or mineral
amygdule
rock cavity