Assignment 3: Matter and Minerals

Introduction

Minerals are defined as naturally occurring, inorganic, solids, with definite chemical composition and a regular, internal crystalline structure. The keys to this definition are the chemical composition and the crystalline structure. Different chemical compositions result in different minerals. A good example is the mineral plagioclase. Plagioclase is a member of the feldspar group, but there is more than one type of plagioclase. Albite and anorthite are two examples. Albite has a chemical composition of  NaAlSi₃O₈, while anorthite's chemical composition is CaAl₂Si₂O₈. Very similar, but different - therefore two different minerals.

Different crystalline structures, or how the atoms and molecules are arranged (orderly internal arrangement of atoms), result in different minerals. A good example is a diamond and graphite. Both minerals are composed of carbon (C). The same chemical composition, but two different crystalline structures - therefore, two different minerals.

Physical Properties

Determination of the actual chemical composition and crystalline structure of a mineral is difficult without the proper equipment. In an introductory level lab, it is impossible for us to determine these two aspects of a mineral. Fortunately, these two aspects determine a mineral's physical properties. How the atoms and molecules are arranged and the strength of the bonding between the atoms result in different physical properties for different minerals. While many minerals share common physical properties, when all of a mineral's physical properties are examined, it often results in a unique set of physical properties that can be used to identify the mineral.

Directions: 

1) This assignment is designed to assist you in learning the concepts of this module as well as assess your understanding and application of the content. 

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