Geology And Geophysics

Best way to Identify the different Types of Rocks



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Of course rocks are everywhere and they come in many forms, from the glassy beauty of volcanic glass or obsidian, to the metallic glint of the metallic rocks, to the magical nature of crystals.

Rocks have two major natures: They are crystals, minerals or combinations of both that were formed under great pressure and over long times. Sometimes the crystals grew large enough, underground, to be seen with the naked eye. Sometimes, the magma reached the atmosphere and cooled far too quickly for the crystals to grow. In most of the rock that we see, either the weathering effects of the atmosphere changed the rock, through wind, acid rain, tumbling, pressure and other chemical and physical actions.

In the rarest events of all, meteors slammed into the earth's surface or nuclear bombs created an incredible substance called "shocked quartz", where the incredible and sudden heat and pressure actually changed the structure of the quartz crystals. Volcanoes cannot produce such conditions.

First, the origin of the rock must be identified. There are three broad classifications: igneous, sedimentary and metamorphic. Igneous rock is formed straight from the magma. Sedimentary rock is igneous rock that was broken down into very fine particles, then subjected to pressure and time. Metamorphic rock is a mixture of igneous and sedimentary rock that formed underground and under great pressure.

Second, studying the ways that heat, pressure, being underground or exposed to the atmosphere led to the formation of various types of rock is very helpful. Rocks tell us a lot about the tumultuous and violent nature of the planet in its past, and they tell us about the workings of the atmosphere, pressure and heat over great periods of time. Then there is water, the chemicals in air, temperature, or weather, that work their magic over great periods of time.

The best way to physically test and examine rocks in the field or at home is to use the classic identification of rocks which uses the five basic observations of hardness, reflective property, color, chemical reaction, and streak and luster.

A good rock identification table , reference book or field pocketbook can lead the way as the scientist examines interesting rocks and notes various properties. The table can be referred to in order to find out where the rock is classified and to come to final conclusions as to its identity. There are a lot of rock hunter's guides that are portable, regional and that have good pictures and information about native rock.

After finding an interesting rock, a notebook as to location (even using the GPS coordinates if possible) is very helpful in determining whether the rock is native or was brought in through some landscaping or construction project.

All is not lost if the rock is non native! A good rock detective can make some inquiries into the vendor who sold the rock. In many cases a legitimate rock vendor is a fountain of information and will be more than glad to help with finding the origins and composition of the mystery rock!

Also, there are excellent "treasure hunt" shows on the cable channels where interesting facts about the surrounding history and origins of a particular gem and even meteorites are provided. Even YouTube has a variety of rock videos that do not involve music!

In summary, learning about rocks in your region or area, then getting out there and doing some rock hunting, then making the study in the home laboratory is a fun and rewarding activity that makes for interesting conversations and the bragging rights that go with interesting collections.





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