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What is a rock?

  1. Sep 15, 2005 #1
    Many people already know the answer to this, but pretend you don't, and if you have never known the answer consider yourself lucky it's a good puzzle.
    How does a stone form, I mean how does it by simple degrees and pressure and time go from a lump of mud to a hard conglomerate of rock or solid stone?
    Could temperature alone form a rock or pressure alone or does it take both motion and pressure? What exactly is pressure doing over such great lengths of time that give this result of something so difficult to break apart? Why does it take so long anyway? Can stones be formed out of any matter with time, heat, and pressure? How do all the atoms know to cling more tightly to each other when in rock form, I mean could one atom on one side of the rock have any sort of bond or intimate relationship with another atom on the other side of the rock?
  2. jcsd
  3. Sep 16, 2005 #2
    Mud stone, Sand stone is a compressed form of the latter caused by pressure of techtonic movement and top sediment pressures placed upon it, Usually there is no high temperatures involved unless it occures in or around volcanic activity or extreme pressures, The Mud stone or Sand stone has a wet and weak bond like wet cement, The Mud stone or Sand stone begins to have a tighter bond when it begins to set under pressure, This can also be done with cement, If Cement is allowed to cure under normal atmospheric conditions it will have a decent bond strength but if the cement is allowed to cure under many atmospheres of pressure the cement will cure faster and also have a denser bond and the cement will have much greater bond strength. Basically it is the crystal formation of its structure becomes more compact, Denser, and a more rigid bond and less water content.

    Hope this helps.
    Last edited: Sep 16, 2005
  4. Sep 16, 2005 #3
    Of course there is also basaltic stone forming, as cooling magma, and sometimes http://home.wanadoo.nl/bijkerk/pebble.jpg [Broken] with year rings.
    Last edited by a moderator: May 2, 2017
  5. Sep 16, 2005 #4
    The conventional divisions of rocks is into sedimentary, igneous and metamorphic.
    Sedimentary rocks may be further subdivided into clastic (conglomerates/breccias, sandstones, siltstones, clays); chemical (evaporites, some limestones); biogenic (limestones). Under the influence of heat, pressure, solutions and probably biological effects, jointly identified as diagenesis, the sediments become rocks. The process of diagenesis merges into that of metamorphism (either regional or thermal), and in some case into igneous, with the formation of granitic rocks, while basalts emerge from partial melting of the upper mantle. Every possible combination of the above can and does keep herds of introverted geologists happy for many years.
  6. Sep 17, 2005 #5
    Hi Ophiolite, long time no see.

    About those introverted geologists:

    Sir Walter Scott, St.Roman1s Well 1824
  7. Oct 9, 2005 #6
    Hello Andre, I missed your response when you made it. I've been mainly over on 'the intelligent forum' insulting idiots. This seems a much nicer place.

    On topic, the answer I gave above was a very geocentric one. On other worlds ice is a rock. We might be better describing a rock as something solid that forms the crust and mantle of planets. (In which category, planets, I include large moons.)
  8. Nov 17, 2005 #7
    But if ice is a mineral, can it also be a rock? (I mean generally, on whichever planet).
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