Geology

• clastic rock

  (geology) a rock composed of broken pieces of older rocks.

• sill

  (geology) a flat (usually horizontal) mass of igneous rock between two layers of older sedimentary...

• xenolith

  (geology) a piece of rock of different origin from the igneous rock in which it is emb...

Also contains

• concretion

  A hard lump produced by the concretion of mineral salts; found in hollow organs or ducts...

• boulder

  A large smooth mass of rock detached from its place of origin.

• outcrop

  The part of a rock formation that appears above the surface of the surrounding land.

• crystal

  A rock formed by the solidification of a substance; has regularly repeating internal structure;...

• chondrite

  A rock of meteoric origin containing chondrules.

• stepping stone

  A stone in a marsh or shallow water that can be stepped on in crossing.

• tor

  A prominent rock or pile of rocks on a hill.

• achondrite

  A stony meteor lacking chondrules.

• pebble

  A small smooth rounded rock.

• bedrock

  Solid unweathered rock lying beneath surface deposits of soil.

• wall rock

  A rock immediately adjacent to a vein or fault.

• petrifaction

  A rock created by petrifaction; an organic object infiltrated with mineral matter and...

• intrusion

  Rock produced by an intrusive process.

• whinstone

  Any of various hard colored rocks (especially rocks consisting of chert or basalt).