Igneous rocks: Rhyolite
By: Jose Juan Gutierrez
Rhyolite is a fine-grained igneous extrusive rock of high silica content or felsic rock. Rhyolite is composed principally of quartz and feldspar minerals, and traces of biotite, plagioclase, mica, amphibiotes, and pyroxenes. It resembles granite in mineral composition, although granite is an intrusive igneous rock...
By: David Jefferson
The current methods for exploitation of mineral concentrations have changed greatly from the those used even a hundred years ago, with the possible exception of the quest for gold or precious gemstones. Advances in geoscience, the invention of aviation, space flight, electronics, computers and the...
Large volcanic rocks discovered floating off New Zealand coast
By: Sun Meilan
Despite all the scientific research that goes on in today’s technical world, nature still manages to surprise scientists sometimes. That is precisely what happened when a floating island of rock, approximately the size of the country of Belgium, or 26,000 square kilometres, was...
Metamorphic rocks: Hornfels
By: J. Lang Wood
Hornfels are part of a group of metamorphic rocks produced under certain natural forces. The word hornfels comes from the German meaning “hornstone” because it was associated with the horn-shaped peaks of the Alps. Hornfels are igneous rocks formed by contact metamorphism, meaning they...
By: Hai Shunxi
Hornfels is a variety of metamorphic rock; which means that the rock's original texture, mineralogy, or both have been changed. The most obvious changes occur in the minerals that make up the rock. Although the rocks never quite melt, some or all of the minerals...
Metamorphic rocks: Gneiss
By: J. Lang Wood
Gneiss rocks are metamorphic rocks that have been altered chemically from existing rocks into a denser type of rock. Compression, plate tectonics, stress and shearing warp and change existing rocks over time. Gneiss is granite that has been changed by these forces into denser rock...
By: Hai Shunxi
Tuffs form an unusual group of rocks that combine the characteristics of two major rock groups, sedimentary rocks and igneous rocks. Like some sedimentary rocks such as sandstone, tuffs consist of deposits of separate particles that are later bonded together to form a solid rock...
By: Hai Shunxi
Amphibolite is a type of metamorphic rock that is rich in minerals of the amphibole group, of which the most common mineral is hornblende. Identification of this type of rock helps earth scientists to reconstruct the region's geologic history based on the conditions under which...
By: Hai Shunxi
If you pick up an ordinary stick and play with it, you'll find that you can bend it only so far before it suddenly breaks. Most substances, including rocks, will also undergo some degree of plastic deformation, bending, before they display brittle deformation: rupture, or...
Common equipment used in geology
By: Francis Harris
Geology is not just an academic study of earth, its rocks and their processes of formation (See Wikipedia Geology) but is a very practical undertaking pursued by professional mineral explorer or surveyor and amateur fossicker alike. There are a few basic tools that are common...

 

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