Broadly speaking, there are three kinds of rocks. They are: sedimentary (e.g. sandstone, limestone, slate and shale), igneous (e.g. granite, basalt) and metamorphic (e.g. marble, gneiss, schist). Sedimentary rocks are typically formed in the presence of water. Limestone often has identifiable organisms (shells, skeletons). Igneous rocks are formed from cooling of molten rock. Metamorphic rocks are formed when rock is transformed under heat and pressure. For example, when limestone can be transformed to marble.

Slang definitions:

  1. rock, noun: a small chunk of crack cocaine. Usage example: Phil and Mary purchased a twenty dollar rock, which they will smoke later this evening.

  • rock, {rocking, rocks, rocked} verb: (often used with up as in rock up -- to turn powdered cocaine into crack cocaine. Usage example: Joan rocked up the whole eight ball of cocaine, so she could make her rent money this month.
  • rock, noun: a term used to describe a tight poker player. Usage example: John is a rock, because he is a patient player that seldom loses money.
  • rock, noun: short for rock and roll. Usage example: Bill and Sue like to dance to rock music.
  • rock, noun: anything that has attributes of strength and sturdiness, particularly used to describe people. Usage example: In their relationship, Juanita always considered Tyrone to be her rock, since he was always strong and dependable. "Thou art Peter, and upon this rock I will build my church." -- Gospel of Matthew--New Testament.
  • rock, {rocking, rocks, rocked} verb: proceeding in a favorable or desirable manner. Usage example: John's team just won four games in a row. They really rock!
  • rock, noun: hard stick bright-colored stick candy often peppermint flavored.
  • rock, noun: The curling stone.

  • rock, noun: The cue ball in billiards or pool games. Usage example: Delbert has a hard time with his cue control today. He keeps letting the rock go wild.
  • A simplistic, animalistic, and yet very popular variety of music, generally based on sexual desire or angst. Major practicioners include: Rock should not be confused with "Rock and Roll", a 1950's term for the genre. As the language evolved (in this case via contraction), "rock and roll" became "rock" at about the same time that the 1950's "rockabilly" genre died out, thereby permanently associating "rock and roll" with a bluesy, country feel.

    The distinction between "rock" and "rock and roll" is a subject of much debate. Some feel there is no distinction while others feel that "rock and roll" is a genre closely associated with the early days of rock.

    Recent developments in rock music (see Limp Bizkit) have seen the genre infused with a wide variety of other genres, especially rap, reggae, and folk.

    Sub-genres include:

    We divide rocks into three basic types: igneous, formed when molten rocks cool down; sedimentary, formed when sediment is deposited at the bottom of the sea; and metamorphic, made when other kinds of rock are transformed by heat and pressure.

    As you probably know, the inside of the Earth is very hot, and rocks deep inside melt in the high temperatures. Molten rock is called magma. When it erupts to the surface, for example in a volcano, we call it lava. When molten rock solidifies, it becomes igneous rock such as granite, made out of interlocking crystals. If the rocks cool slowly, as they sometimes do deep within the Earth's crust, these crystals are large, because they have a lot of time to grow. If they cool quickly, like lava does when it hits the cold air or sea water, there is little time for the crystals to grow, so they are very small. Igneous rocks tend to be very hard.

    Sedimentary rocks are formed from grains, deposited on the sea bed in layers, and compacted by the pressure of the sea. The grains might come from other rocks that have been eroded by the sea or the weather, or they might be hard, left-over bits of long-dead organisms. Chalk is mostly made of the shells of microscopic organisms called coccolithophores, for example. It is quite common to find fossils of larger animals deposited in sedimentary rocks such as limestone. Because they are made of little bits of things, only loosely pressed together, sedimentary rocks tend to be far weaker than other kinds of rock, and they are very susceptible to erosion.

    Metamorphic rocks are formed when other kinds of rock are transfomed (metamorphosed) by heat and pressure within the Earth's crust – enough to bring about profound changes in their chemistry and structure, but not enough to melt them. The presence of water and the effects of strain are also important here. Because there are so many different factors deciding the final form of the rock, metamorphic rocks are incredibly varied. They are usually hard, having been subjected to great heat and pressure, and often stripy or banded due to shear forces causing them to change shape as they formed.

    Rock (?), n.

    See Roc.


    © Webster 1913.

    Rock, n. [OE. rocke; akin to D. rok, rokken, G. rocken, OHG. roccho, Dan. rok, Icel. rokkr. Cf. Rocket a firework.]

    A distaff used in spinning; the staff or frame about which flax is arranged, and from which the thread is drawn in spinning.


    Sad Clotho held the rocke, the whiles the thread
    By grisly Lachesis was spun with pain,
    That cruel Atropos eftsoon undid.


    © Webster 1913.

    Rock, n. [OF. roke, F. roche; cf. Armor. roc'h, and AS. rocc.]


    A large concreted mass of stony material; a large fixed stone or crag. See Stone.

    Come one, come all! this rock shall fly
    From its firm base as soon as I.
    Sir W. Scott.

    2. Geol.

    Any natural deposit forming a part of the earth's crust, whether consolidated or not, including sand, earth, clay, etc., when in natural beds.


    That which resembles a rock in firmness; a defense; a support; a refuge.

    The Lord is my rock, and my fortress.
    2 Sam. xxii. 2.


    Fig.: Anything which causes a disaster or wreck resembling the wreck of a vessel upon a rock.

    5. Zool.

    The striped bass. See under Bass.

    This word is frequently used in the formation of self-explaining compounds; as, rock-bound, rock-built, rock-ribbed, rock-roofed, and the like.

    Rock alum. [Probably so called by confusion with F. roche a rock.] Same as Roche alum. -- Rock barnacle Zool., a barnacle (Balanus balanoides) very abundant on rocks washed by tides. -- Rock bass. Zool. (a) The stripped bass. See under Bass. (b) The goggle-eye. (c) The cabrilla. Other species are also locally called rock bass. -- Rock builder Zool., any species of animal whose remains contribute to the formation of rocks, especially the corals and Foraminifera. -- Rock butter Min., native alum mixed with clay and oxide of iron, usually in soft masses of a yellowish white color, occuring in cavities and fissures in argillaceous slate. -- Rock candy, a form of candy consisting of crystals of pure sugar which are very hard, whence the name. -- Rock cavy. Zool. See Moco. -- Rock cod Zool. (a) A small, often reddish or brown, variety of the cod found about rocks andledges. (b) A California rockfish. -- Rock cook. Zool. (a) A European wrasse (Centrolabrus exoletus). (b) A rockling. -- Rock cork Min., a variety of asbestus the fibers of which are loosely interlaced. It resembles cork in its texture. -- Rock crab Zool., any one of several species of large crabs of the genus Cancer, as the two species of the New England coast (C. irroratus and C. borealis). See Illust. under Cancer. -- Rock cress Bot., a name of several plants of the cress kind found on rocks, as Arabis petraea, A. lyrata, etc. -- Rock crystal Min., limpid quartz. See Quartz, and under Crystal. -- Rock dove Zool., the rock pigeon; -- called also rock doo. -- Rock drill, an implement for drilling holes in rock; esp., a machine impelled by steam or compressed air, for drilling holes for blasting, etc. -- Rock duck Zool., the harlequin duck. -- Rock eel. Zool. See Gunnel. -- Rock goat Zool., a wild goat, or ibex. -- Rock hopper Zool., a penguin of the genus Catarractes. See under Penguin. -- Rock kangaroo. Zool. See Kangaroo, and Petrogale. -- Rock lobster Zool., any one of several species of large spinose lobsters of the genera Panulirus and Palinurus. They have no large claws. Called also spiny lobster, and sea crayfish. -- Rock meal Min., a light powdery variety of calcite occuring as an efflorescence. -- Rock milk. Min. See Agaric mineral, under Agaric. -- Rock moss, a kind of lichen; the cudbear. See Cudbear. -- Rock oil. See Petroleum. -- Rock parrakeet Zool., a small Australian parrakeet (Euphema petrophila), which nests in holes among the rocks of high cliffs. Its general color is yellowish olive green; a frontal band and the outer edge of the wing quills are deep blue, and the central tail feathers bluish green. -- Rock pigeon Zool., the wild pigeon (Columba livia) Of Europe and Asia, from which the domestic pigeon was derived. See Illust. under Pigeon. -- Rock pipit. Zool. See the Note under Pipit. -- Rock plover. Zool. (a) The black-bellied, or whistling, plover. (b) The rock snipe. -- Rock ptarmigan Zool., an arctic American ptarmigan (Lagopus rupestris), which in winter is white, with the tail and lores black. In summer the males are grayish brown, coarsely vermiculated with black, and have black patches on the back. -- Rock rabbit Zool., the hyrax. See Cony, and Daman. -- Rock ruby Min., a fine reddish variety of garnet. -- Rock salt Min., cloride of sodium (common salt) occuring in rocklike masses in mines; mineral salt; salt dug from the earth. In the United States this name is sometimes given to salt in large crystals, formed by evaporation from sea water in large basins or cavities. -- Rock seal Zool., the harbor seal. See Seal. -- Rock shell Zool., any species of Murex, Purpura, and allied genera. -- Rock snake Zool., any one of several large pythons; as, the royal rock snake (Python regia) of Africa, and the rock snake of India (P. molurus). The Australian rock snakes mostly belong to the allied genus Morelia. -- Rock snipe Zool., the purple sandpiper (Tringa maritima); -- called also rock bird, rock plover, winter snipe. -- Rock soap Min., a kind of clay having a smooth, greasy feel, and adhering to the tongue. -- Rock sparrow. Zool. (a) Any one of several species of Old World sparrows of the genus Petronia, as P. stulla, of Europe. (b) A North American sparrow (Pucaea ruficeps). -- Rock tar, petroleum. -- Rock thrush Zool., any Old World thrush of the genus Monticola, or Petrocossyphus; as, the European rock thrush (M. saxatilis), and the blue rock thrush of India (M. cyaneus), in which the male is blue throughout. -- Rock tripe Bot., a kind of lichen (Umbilicaria Dillenii) growing on rocks in the northen parts of America, and forming broad, flat, coriaceous, dark fuscous or blackish expansions. It has been used as food in cases of extremity. -- Rock trout Zool., any one of several species of marine food fishes of the genus Hexagrammus, family Chiradae, native of the North Pacific coasts; -- called also sea trout, boregat, bodieron, and starling. -- Rock warbler Zool., a small Australian singing bird (Origma rubricata) which frequents rocky ravines and water courses; -- called also cataract bird. -- Rock wren Zool., any one of several species of wrens of the genus Salpinctes, native of the arid plains of Lower California and Mexico.


    © Webster 1913.

    Rock (?), v. t. [imp. & p. p. Rocked (?);p. pr. & vb. n. Rocking.] [AS. roccian; akin to Dan. rokke to move, to snake; cf. Icel. rukkja to pull, move, G. rucken to move, push, pull.]


    To cause to sway backward and forward, as a body resting on a support beneath; as, to rock a cradle or chair; to cause to vibrate; to cause to reel or totter.

    A rising earthquake rocked the ground.


    To move as in a cradle; hence, to put to sleep by rocking; to still; to quiet.

    "Sleep rock thy brain."


    Rock differs from shake, as denoting a slower, less violent, and more uniform motion, or larger movements. It differs from swing, which expresses a vibratory motion of something suspended.


    © Webster 1913.

    Rock, v. i.


    To move or be moved backward and forward; to be violently agitated; to reel; to totter.

    The rocking town
    Supplants their footsteps.
    J. Philips .


    To roll or saway backward and forward upon a support; as, to rock in a rocking-chair.


    © Webster 1913.

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