Chapter 2 Notes - Chapter 2 Notes The Earths Structure Of...

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Chapter 2 Notes The Earth’s Structure Of the three structural layers of Earth (core, mantle, crust) it is the crust which is of prime interest, as this is the birthplace of gem minerals and its geology is the key to their formation Minerals and Rocks A mineral is a substance which has been formed within the Earth by the forces of inorganic nature It is also a homogeneous, or uniform, substance with a definite atomic structure, and has a chemical formula and a set of physical and optical characteristics which are constant throughout its bulk Only 60 minerals have the necessary qualities of beauty, rarity and durability to make them suitable for use as gem materials Although minerals are mined from the Earth’s crust in various states of purity, the bulk of this crust is made of various mixtures of minerals, and these mixtures or aggregates are called rocks The Formation of Rocks in the Earth’s Crust Sedimentary Rocks The upper and most thinnest layer of the earth’s crust is composed mainly of the fine deposits of sand, grit and clay eroded by action of rain, wind and flowing water from the ancient pre-existing rocks in the middle layer of the crust, and compressed to form layers of sandstone or limestone Because of their formation, these top layer rocks are called sedimentary Igneous Rocks The middle layer of the crust is formed by the solidification of molten magma and is composed of rocks which are described as igneous (mostly granite)
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This note was uploaded on 10/11/2010 for the course ECONOMICS ECON 1B03 taught by Professor Holmes during the Fall '08 term at McMaster University.

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Chapter 2 Notes - Chapter 2 Notes The Earths Structure Of...

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