GO 324 Rocks and Minerals
ES 567A Hand Specimen Petrology
Dr. Susan Ward Aber


Emporia State University
Emporia, Kansas USA
Earth Science Department

Introduction to Rocks

Rock and minerals were important resources in the development of human civilizations and continue to be essential to modern existence. There is evidence for widespread mining of flint some 50,000 years ago (Schumann, 1993, p. 187). These relatively abundant natural resources have been used as both functional and ornamental materials. Functional examples of rock are found in tools, weapons, and architecture, whereas ornamental uses range from jewelry to a canvas for painting as in cave art or petroglyphs.

Rocks are a natural aggregate of one or more minerals. The study of rocks draws upon mineralogy, geology, paleontology, chemistry, and physics. Ascertaining the textures, structures, mineral components, and organic remains when present are all key to identifying rocks. Mineral components and organic remains may be determined with the unaided eye, but often times positive identification will require high magnification or devices more sophisticated than a microscope. Texture refers to the size, shape, and arrangement of component constituents. Structure may describe the shape, dimensions and articulation of the component constituents (Simon & Schuster, 1978, p. 415). Textural and structural terms may vary with different rock classifications. Structures are usually visible on a geologic scale, whereas textures are on a hand specimen scale. Texture is the result of the formational environments and structures, the result of deformations.

There are three classifications of rocks found on Earth: igneous, sedimentary, and metamorphic. Earth is divided into a crust, mantle, and core, with the upper mantle and crust together referred to as the lithosphere. The lithosphere is divided into plates that are bounded by faults, subduction zones, and spreading centers. Even though the oceanic crust is primarily basalt and continental crust is primarily granite, the upper 10 miles of the lithosphere consists of 95% igneous or their metamorphic equivalents, 4% shale, 0.75% sandstone, and 0.25% limestone (Klein and Hurlbut, 1999, p. 221). Therefore, igneous and metamorphic rocks dominate the lithosphere volumetrically and sedimentary rock is primarily exposed as a thin covering over much of the Earth's continents. Raymond (1995) stated that a thin veneer of sedimentary rock covers 66% of the continental crust, while the remaining surficial exposures are equally divided between igneous and metamorphic (p. 3).

More can be found at Identifying Rocks in Kansas and Colorado, http://www.geospectra.net/fieldgeology/rocks.htm. Igneous, sedimentary, and metamorphic rock identification clues can be found at http://www.geospectra.net/fieldgeology/rocks.htm#igneous and rock images are on the same page, http://www.geospectra.net/fieldgeology/rocks.htm#images. For interesting and animated views of rock cycle and rock processes visit websites sent in by students:

Oooo an optional opportunity for you! Can you guess how deep into the mantle we have seen? Which minerals are found in these deep seated rocks? To answer these questions, visit World's Deepest Rocks Recovered, http://news.bbc.co.uk/1/hi/sci/tech/755631.stm. If you are enrolled in the course, send a paragraph summary of the website and answer the question! Email me, esu.abersusie@gmail.com with the report for one extra-credit point on the second exam. Place GO 324 second exam point in the subject line of the email, and I must receive this by the second test.

Suggested Reading and Interesting Links


To the beginning!

Petrology Introduction
Sedimentary Rock
Metamorphic Rock
Course Field Trip
Course Syllabus
Class and Field Trip Specimen Collection

This page originates from the Earth Science department for the use and benefit of students enrolled at Emporia State University. The curriculum is © by the author, 2001-2013. Creation and last update January, 2013. For more information contact the course instructor, S. W. Aber, e-mail: esu.abersusie@gmail.com.

To understand copyright, visit www.copyright.gov/. All rights reserved. Susan Ward Aber.