Difference between revisions of "Crystal Systems"
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! Examples | ! Examples | ||
|- | |- | ||
− | | '''Cubic''' <br> | + | | '''Cubic''' <br /> |
− | The cube is composed of 6 square faces<br> | + | The cube is composed of 6 square faces<br /> |
− | at 90° angles to each other. Each<br> | + | at 90° angles to each other. Each<br /> |
− | face intersects one of the crystallographic<br> | + | face intersects one of the crystallographic<br /> |
− | axes and is parallel to the other two.<br> | + | axes and is parallel to the other two.<br /> |
− | | [[image: | + | | [[image:cubic.jpg]] |
|[[Diamond]] <br /> | |[[Diamond]] <br /> | ||
[[Garnet]] <br /> | [[Garnet]] <br /> | ||
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| '''Tetragonal''' <br /> | | '''Tetragonal''' <br /> | ||
− | The tetragonal system also has three axes<br> | + | The tetragonal system also has three axes<br /> |
− | that all meet at 90°. It differs from the<br> | + | that all meet at 90°. It differs from the<br /> |
− | isometric system in that the C axis is longer<br> | + | isometric system in that the C axis is longer or<br /> |
− | than the A | + | shorter than the A axes,<br /> |
− | + | which are the same length.<br /> | |
− | | [[image: | + | | [[image:tetragonal.jpg]] |
− | | [[Zircon]] | + | |[[Zircon]] |
|- | |- | ||
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In the hexagonal system, we have an additional axis,<br> | In the hexagonal system, we have an additional axis,<br> | ||
giving the crystals six sides. Three of these<br> | giving the crystals six sides. Three of these<br> | ||
− | are equal in length and meet at | + | are equal in length and meet at 120° to each other. <br> |
− | The C or vertical axis is at 90° to the | + | The C or vertical axis is at 90° to the horizontal axes.<br> |
Mineralogists sometimes divide this into two systems, <br> | Mineralogists sometimes divide this into two systems, <br> | ||
the hexagonal and the trigonal, based on their external<br> | the hexagonal and the trigonal, based on their external<br> | ||
appearance (see following). | appearance (see following). | ||
− | |[[image: | + | |[[image:hexagonal.jpg]] |
|[[Aquamarine]]<br /> | |[[Aquamarine]]<br /> | ||
− | |||
[[Beryl]] <br /> | [[Beryl]] <br /> | ||
[[Emerald]]<br /> | [[Emerald]]<br /> | ||
[[Heliodor]]<br /> | [[Heliodor]]<br /> | ||
[[Morganite]]<br /> | [[Morganite]]<br /> | ||
+ | [[Apatite]] | ||
|- | |- | ||
| '''Trigonal'''<br /> | | '''Trigonal'''<br /> | ||
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therefore some gem references will list these as<br /> | therefore some gem references will list these as<br /> | ||
hexagonal. | hexagonal. | ||
− | | [[image: | + | | [[image:trigonal.jpg]] |
− | | [[Amethyst]]<br /> | + | |[[Amethyst]]<br /> |
+ | [[Benitoite]]<br /> | ||
[[Citrine]]<br /> | [[Citrine]]<br /> | ||
[[Corundum]]<br /> | [[Corundum]]<br /> | ||
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In this system, there are three axes all of which<br /> | In this system, there are three axes all of which<br /> | ||
meet at 90° to each other. However, all the axes<br /> | meet at 90° to each other. However, all the axes<br /> | ||
− | are | + | are of different length. |
− | | [[image: | + | |[[image:Orthorhombic.jpg]] |
|[[Alexandrite]]<br /> | |[[Alexandrite]]<br /> | ||
[[Andalusite]]<br /> | [[Andalusite]]<br /> | ||
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The above crystal systems all have axes sides<br /> | The above crystal systems all have axes sides<br /> | ||
that meet at 90°. In the monoclinic system, all<br /> | that meet at 90°. In the monoclinic system, all<br /> | ||
− | the axes are different lengths. | + | the axes are different lengths. The A axis is inclined<br /> |
− | the | + | to the C axis. The B axis is at 90° to them. <br /> |
− | one | + | |
− | | [[image: | + | You can imagine this as a matchbox that slants to one side. |
+ | |[[image:monoclinic.jpg]] | ||
|[[Azurite]]<br /> | |[[Azurite]]<br /> | ||
[[Diopside]] <br /> | [[Diopside]] <br /> | ||
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In this system all the axes are different <br /> | In this system all the axes are different <br /> | ||
lengths and none of them meet at 90°. | lengths and none of them meet at 90°. | ||
− | | [[image: | + | |
+ | You can imagine this as a matchbox which slants to two sides. | ||
+ | | [[image:triclinic.jpg]] | ||
|[[Turquoise]] | |[[Turquoise]] | ||
|} | |} | ||
+ | <br > | ||
+ | '''Next:[[Form| Form]]''' | ||
+ | <br /><br /> | ||
+ | '''[[Table_Of_Contents| Return to the Table of Contents]]''' |
Latest revision as of 11:42, 13 December 2012
Crystal System | Diagram | Examples |
---|---|---|
Cubic The cube is composed of 6 square faces |
Diamond | |
Tetragonal The tetragonal system also has three axes |
Zircon | |
Hexagonal
In the hexagonal system, we have an additional axis, |
Aquamarine | |
Trigonal The trigonal system is a subsystem of the |
Amethyst | |
Orthorhombic In this system, there are three axes all of which |
Alexandrite Andalusite | |
Monoclinic The above crystal systems all have axes sides You can imagine this as a matchbox that slants to one side. |
Azurite | |
Triclinic In this system all the axes are different You can imagine this as a matchbox which slants to two sides. |
Turquoise |