1.    Central Displays

These proceed clockwise around the room from the entry point from the first floor, or from the elevator.  The content follows a traditional scientific logic.

1.1    Introduction

Welcome!!!

            In this room you will learn about minerals, crystals, gems, and rocks.  These items are of great interest and value to society.  In the display cases in this central part of the room you will be following a logical, connected, sequence of displays.  The specialized wall displays highlight robust portions of minerals and of the Museum collections.

            Minerals are what makes up the solid earth, because rocks are just mixtures of minerals.  Rocks and minerals are everywhere.  Crystals and gems are special and are highly prized.  Crystals form by natural processes and are dug out of the ground by miners or crystal collectors.  The flat faces you see on a crystal were not made by man, but by Mother Nature.  Fine crystals are works of art.  Gems or gemstones have been cut and worked by jewelers, and are objects of great beauty.

            In the display that follows, minerals will be presented first, and they will be followed by crystals and gems.  At the end, rocks will be discussed  briefly and displayed.  There is also a display of meteorites, which are rocks which fell from the sky and originated from other planets in the outer space.

1.1.1   Quartz Crystal (SiO₂)

            This is a quartz crystal. Although the mineral crystallizes in a great variety of habits or external forms, the one here is common.  Quartz crystals can be very pretty, and they have long been prized by people. In the western European historical tradition, quartz crystal was first mentioned by Pliny in his book on natural history in 77 A.D.

            The crystal faces on this sample were naturally formed by Mother Nature; they are not cut by a jeweler or diamond cutter.  These are the natural growth faces of the quartz in an open cavity underground.  These are the last or terminal surfaces upon which quartz crystal growth took place.  They are splendent and mirror-like.

            An entire cabinet in this room has been devoted to the quartz family of minerals.  You have got to check it out, behind you!

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1.1.2    Synthetic Quartz

            This crystal of silicon dioxide (SiO2) has been grown in a laboratory, and consequently it does not classify as a mineral (see item #1 in definitions below).  In most other ways this sample has the properties of quartz.  This was grown in the laboratory as an overgrowth of an already existing thin slice of actual quartz.  That thin slice, or seed crystal, can be seen as a horizontal plane at the center of the sample.  Remnants of the brackets which held up the seed during the hydrothermal (hot water) conditions of crystal growth can be seen at the opposite ends of the seed crystal.  The textures of the different surfaces indicate different growth mechanisms on each surface.  Crystal growth is a fascinating science.

 1.1.3    What is a Mineral?

            The world is divided chemically into 91 different natural substances called chemical elements.  Their study is part of the science of chemistry, and they are the materials that make up rocks and minerals.  They are organized according to their properties into the periodic chart of the chemical elements.

            Chemicals come together by the formation of chemical bonds and form chemical compounds.  These are formed by combining these 91 elements in all sorts of different ways.  Some common and simple chemical compounds are water (H 2O), and salt (NaCl).  More complicated chemical compounds are steel, your bones and teeth, and most solid materials around you.  An extremely complicated compound would be DNA, which constitutes part of the genetic material of the cells of your body.

            Chemical compounds which have formed by natural processes but also inorganic (non-living) processes are called MINERALS.

            Minerals specifically refer to things formed by non-living processes, because things formed by living processes, plants, animals, and you, are the subject of the science of biology.

Strictly speaking, the definition of a mineral is as follows:

            1.        Naturally occurring; produced by Mother Nature

            2.        Inorganic, not produced by living processes.

            3.        Solid material not liquid or gas.

                       4.       Specific, geometric, arrangements of chemical elements, which is 

                       called the crystal structure.

            5.        Specific chemical composition, expressed by its chemical formula.

            Why are minerals important?  Well, they are a major and vital initial input of materials into our society.  They have economic value, and are the raw resources for part of our economy.  But minerals also are beautiful.  Crystals are formed by nature and are one of Mother Nature's works of fine art.  Gem stones are minerals which have been cut and fashioned into faceted stones or rounded cabochons by man to bring out or enhance their beauty.

            Finally, another important thing about minerals is that they help us understand the earth.  Rocks, of which the solid earth is made, are nothing more than mixtures of minerals.  Understanding minerals leads to the ability to understand rocks.

            In 2000 there were approximately 3600 different minerals known in the world.  The small booklet entitled "Glossary of Mineral Species" gives a list and chemical formula of all known minerals.  Minerals are sometimes named after people or places.  The last three letters of all new mineral names are "ite".  Scientists discover about 100 new minerals each year.  Instruments with which these discoveries can be made are located in the Department of Geological Sciences here at UTEP.  The electron microprobe is one of these instruments.

            A surprising thing about mineralogy, the study of minerals, is that there are so few minerals.  Consider the millions or billions of possible and real chemical compounds made from the 91 different chemical elements.  And yet, there are only 3600 different minerals.  Mother Nature must have something unusual going on!

            One of the first things that people do with knowledge is to classify, categorize, and pigeon-hole it.  Let us consider the 3600 different minerals which exist.  How do we break them down, or simplify them, so that we can understand them?  After much study it was found the best way to classify them scientifically is according to the anion (negatively charged chemical element or molecule) in the chemical formula.

            The mineralogical classification used in the displays in this room at the Centennial Museum is the standard scientific one based on the anions in the chemical formula.  It is called Dana's System after J. D. Dana, who devised it in 1837.  The categories that follow, and the specimens in the displays in the center of the room are organized in this sequence.  They are listed as 1.2 to 1.12 in the Table of Contents.

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1.2    Native Elements

            These minerals are not chemical compounds, but are the pure, 'native' elements existing as a mineral.  Gold (Au) and diamond (carbon, C) are the most important members of this family.  Jewelry characterizes the uses of some native elements.

1.2.1                                  Native Gold

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1.2.2                            Native Copper

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1.2.3                      Native Sulfur

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1.3 Sulfides

            This family is characterized by chemical compounds having anions of sulfur.  There are many minerals in this group, but they are not common.  Pyrite (FeS₂), also known as fool's gold, is the most common of this group.  Sulfides constitute the most important ores or sources of the following metals which are essential to our economic and industrial complex: copper, lead, zinc, nickel, cobalt, molybdenum, rhenium, vanadium, germanium, gallium, and many others.  Magmatic and hydrothermal (hot water) geologic environments often contain significant concentrations of sulfides.  Sulfides are very 'productive' in providing many resources useful to man, however they and their oxidation present severe environmental problems.

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1.3.1 Galena  

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1.3.2 Stibnite

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2.4    Sulfosalts

            This mineralogical family is a subdivision of the sulfides, but the group is important enough to indicate separately.  They are made up of simple metal sulfide components such as lead (PbS), copper (Cu₂S) and silver (Ag₂S) in combination with semimetal sulfide components of arsenic, antimony or bismuth (As₂S₃,Sb₂S₃, Bi₂S₃).  Their physics and chemistry exhibit incredible diversity, and there are even cylindrical and ring shaped crystals.

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Tetrahedrite and Pyrite

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Jamesonite and Pyrite

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Bismuthinite and Barite

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Sulfosalt cabinet

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