|
|
.-Rock
Gallery --.--Mineral groups -------Greeting cards ---------Minerals by name ----------Rock and gem shows ---------Mineral locations -------Rockhounding and Mineral Forums ----Dealer stores -What's new |
Welcome
to the
Mineral Library Following is a list of the most popular minerals with specific samples on each item by clicking them.
|
---
|
||||||
 |
 |
 |
 |
 |
 |
 |
| a |
| MINERAL INFORMATION
Rocks are made up of one or more minerals. The individual minerals that compose rocks have specific identifying properties such as hardness, crystal shape, reaction with hydrochloric acid, and the color of the powdered mineral when scratched on a streak plate. Some properties are more useful than others to identify the mineral, depending on the mineral. The shape (not size, though) of a mineral crystal is commonly helpful in identifying the mineral. Colors of some minerals are useful for identifying the minerals, but in other minerals color is very misleading. Many minerals can have different colors. For example, the mineral quartz comes in white, pink, purple, and gray colors. The types and relative proportion of minerals that occur together in a rock tell scientists the story of how that rock was formed. Rocks are named based on how they formed, and by the types, amounts and sizes of minerals in the rocks. One of the most important skills a geologist needs when studying a rock is the ability to observe and describe what he or she sees. Our civilization is heavily dependent on geologic materials for constructing roads, bridges, buildings, and monuments. Each year, the U.S. consumption of geological materials is many tons per person . This includes a great amount of stone. Stone used for building can be found in virtually any city or town, sometimes in a great many varieties. Minerals are crystalline. Crystalline structures are characterized by an ordered internal arrangement of atoms or molecules. The external shape of a mineral may or may not reflect this ordered structure. If a mineral is in the form of a crystal its external form reflects its internal structure. Quartz is commonly found as crystals and as fractured pieces that do not have a crystal form. It is not necessary to understand the concept of what atoms and molecules are, but you should understand the concept of ordered structure. An analogy of stacking blocks (or some other object) in a regular pattern is ordered structure. Rocks are composed of mineral grains. Some sedimentary rocks contain, or are composed completely of, minerals that crystallize from concentrated seawater. These include rock gypsum and rock salt (halite). Igneous rocks are those that solidify from molten material. Grain (crystal) size in igneous rocks is controlled by rate of cooling. If a magma (molten material) cools slowly crystals will grow to a visible size resulting in the coarse-grained texture characteristic of such rocks as granite. If a magma cools quickly (at or near the surface of the earth) crystals will be quite small, resulting in the fine-grained texture of rocks such as basalt. Minerals are the ingredients that make up rocks. It is easy to understand then, that some of the characteristics of the different types of rocks are a result of their mineral composition. Many minerals are valued by people because of the specific qualities or characteristics they display. Minerals are usually formed by inorganic processes, are crystalline solids (have an internal orderly arrangement of atoms), have specific chemical compositions (chemical formula), and have specific physical and chemical characteristics. Minerals are commonly identified by the physical properties they possess. These physical properties include hardness, color, crystal shape, specific gravity (a measure of heaviness), and streak (the color of the mineral in the powdered form). Some other useful properties are reactions with hydrochloric acid and a characteristic taste. |
.