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Note for Engineering Geology - EG By Indrajit Indrajit

  • Engineering Geology - EG
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What is a Mineral? A naturally occurring, inorganic solid that has a definite chemical composition and/or crystal structure Sachikanta Nanda

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Formation & Composition • Minerals come from cooled magma • 2500 kinds of minerals; some are easy to find and others are rare. Sachikanta Nanda

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• Mineral Properties Each type of mineral has its own combination of properties that identify it. Some of the properties are Color Many minerals come in a wide variety of colors. Different minerals can be the same color. It is difficult to use just color to identify a mineral. Streak Streak is the color of a mineral in powdered form. You can see a mineral’s streak by rubbing a sample across an unglazed ceramic plate and observing the powder left behind. Sometimes a mineral’s streak is very different from the color of the sample. Hardness Hardness is the resistance of a mineral to scratching. Geologists use the Mohs' hardness scale to seriate and compare mineral hardness. Sachikanta Nanda

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Specific gravity Specific gravity is the ratio of the weight of a given volume of a mineral to the weight of an equal volume of water. Higher specific gravity means the mineral is heavier. Cleavage Cleavage is how a mineral breaks. Some minerals break in smooth, flat surfaces at identifiable angles, such as calcite. Others fracture and produce no flat surfaces, such as quartz. Fracture Fracture is how a mineral breaks when no cleavage surfaces form. For example, quartz breaks in a pattern known as conchoidal fracture. Conchoidal fracture looks like smooth, curved surfaces. Luster Luster is how a mineral reflects light or how it shines. Some ways to describe luster include glassy or vitreous, metallic, dull, and pearly. Sachikanta Nanda

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