Geology, Part 2

These are the three categories of rocks and minerals: Igneous, Sedimentary, and Metamorphic.  This is what I’ve learned about them.


Igneous rocks are rocks that were melted and then it hardened.  The word igneous comes from the latin word ignis meaning “fire”.  A lot of the earth’s crust is made up of feldspar, mica, and hornblende mixed in.


Sedimentary rocks makes up most of our cliffs.  Sedimentary rocks contain most of the worlds fossils and petrified wood. Shale is made up of cemented particles of clay and a little bit of silt.  Sandstone has particles that are just big enough to see and are made mostly of quartz sand.  Conglomerate has bigger pebbles-bolders that are cemented together.

There are 2 types of chemical sedimentary rocks, Organic and Inorganic.  Organic comes from things that were once living, and inorganic are made up of things that were never living.  Organic limestone has some inorganic limestone, but most of it is organic.  Chalk is made from the shells of single celled organisms that have been deposited.  Coal is the altered remains of huge masses of buried plant material.

Inorganic limeston is made the same way as stalactites and stalagmites.  They form were the water has a great deal of mineral material dissolved in it such as in caves or around mineral springs.  Dolomite is a rock similar to limestone, with atoms of magnesium.  When sea water evaporates, it leaves behind solid minerals like salt.


The greek word meta means “change”, and morphe means “form”.  These 2 words put together means “to change form”, some rocks will metamorphose into something different.  When shale gets heated it turns into slate, which is used for blackboards.  Some people think that schist is metamorphosed slate but they are not quit sure yet.  Gneiss (pronounced nice) is a highly metamorphosed rock with bands of different colors. Limestone changes into marble and  marble is very pretty especially when it is polished.


One thought on “Geology, Part 2

  1. Hi Risa,
    A couple of quick comments – Since learning the three basic rock types as a kid and in college, I have come to reevaluate a few things. #1 is that geologists have never seen granite, grouped as an igneous rock, in the process of forming. In fact when granite is melted, it becomes rhyolite, a volcanic rock. So, why do geologists group granites as igneous rocks? Because their belief is that granites formed from magma and cooled over millions of years. It is part of their belief system about the history of the earth. I have regrouped rocks like granite, gabbros, diorite, granodiorite and the like into Plutonic rock which describes them as basement rocks and coarse-grained rocks. Their formation has not been observed. The true igneous rocks are volcanic rocks. We have seen those forming and they appear to be melts of the plutonic rocks. Metamorphic rocks have also not been seen to be forming. Although geologists talk confidently about their formation, their formation have not been observed. But they do seem to have gone through some kind of change. I related this change to the great tectonic forces of the Flood, not to millions of years of slow change from heat and pressure. They probably did undergo a lot of heat and pressure, but I believe they did so during and for a short time after the Flood. We also cannot account for the great deposits of sedimentary rock some of which is thousands of feet thick. Again, geologists have by and large not seen sedimentary rocks in the process of formation. We just see the vast amounts of sedimentary rocks, most likely laid down during the year-long Flood. Anyway, my thoughts.
    Patrick Nurre
    Northwest Treasures


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