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Spelunking is one of the most interesting things you can possibly do! And to be a good spelunker, you must first know your cave terms! What is spelunking, you say? It's climbing around in caves, exploring the mysteries of those big caverns under the earth. For an explanation of caving terms, visit the Caver's Glossary. Stalactites cling tight to the ceiling of caves. Stalagmites grow from the floor of the cave. Stalagtites and stalagmites are formed over a period of years, usually hundreds of years, usually by the mineral Calcite, by water dripping from the ceiling of the cave. Each little droplet of water holds a tiny grain of sand or rock, and when the water falls to the floor (or drops from the ceiling), the tiny little grain of sand sticks to the floor (or ceiling). The stalactites and stalagmites are formed by years and years and years and years of grains of sand built up on each other. Think of it: drop by tiny drop, grain by tiny grain, these huge formations are made! It takes about a hundred years for the stalactites/mites to grow an inch!! If you ever visit a cave, make sure
you absoloutely DO NOT touch stalactites/mites. Oil on your fingertips sticks to the formation, and every time water drops onto the stalactite/mite from then on, the grain of sand will slide off, instead of sticking, and the stalactite/mite will stop growing. And that would be awful!
There are lots of ways to classify crystals: Crystal groups, Crystal classes, Crystal habits, Crystal lattice, Crystal structure, Crystal symmetry, Crystal faces, and Crystal angles, just to name a few. But I suspect what you're looking for is the Crystal system. This includes six forms: Isometric, Tetragonal, Hexagonal (which includes Trigonal), Orthorhombic, Monoclinic, and Triclinic (aren't you impressed I remembered all those? I sure am). 'Isometric' describes any mineral equal in all three dimensions. 'Tetragonal' minerals have two axes (planes, or planes of symmetry) equal in length, with the third one unequal; all axes are at 90 degrees to each other. 'Hexagonal' crystals have four axes, three of which must be equal in length, and be at a 120 degree angle from the others (the fourth axis can be of differing length, but must be at a right angle). 'Hexagonal' includes 'Trigonal' (which I suspect is your missing seventh form), and just means that the mineral must have six planes of symmetry, whereas the Hexagonal only needs three. 'Orthorhombic' means that the mineral has three axes, all unequal in length and at 90 degrees to one another. 'Monoclinic' is quite common among micas, and describes a mineral with three axes of unequal length, two of which are at right angles to each other, with a third at any angle which is not 90 degrees. 'Triclinic' is a mineral with three axes all of unequal length without any at right angles. You see, I can be technical and serious when I have to be!
Neill's Geology: Gemmologists
You may want to try The Crystal Wheel for some basic information. There's also a really fun game, Pick a Pair o' Crystals, at the 'Dynamic Earth' site.
Well, Hetty, I don't know what you're using to brush your teeth, but I can tell you all about minerals. First off, those bad boys all have properties: Hardness! Streak! Color! Crystal Group! Chemical Group! Luster! Specific Gravity! Cleavage! Fracture! Tenacity! And my personal favorite, Elemental Affiliations! Sound confusing? Don't worry, I'm not going to test you on it. I've got to tell you, though, there are hundreds and hundreds minerals, all of them really, really cool, from Acanthite to Zoisite. Did you know water was a mineral? I bet you've heard it called H2O before, but didn't really know what that meant. Well, it means that for every 2 atoms of the element Hydrogen (H), there is one atom of the element Oxygen (O). So, it's a combination of 2 elements: that's what minerals are! A combination of two or more elements! Isn't that super cool? There are 112 elements, and they can combine all sorts of ways to make different minerals. Some of the cooler minerals (aren't they all cool, though?) are Television Stone (aka Ulexite), which comes in sheets of rock. When you polish it up and stick something under it, it looks like the thing underneath is on top of the rock! Arsenic is another cool one. It's a poison found in weed killer and rat poison, and is often used in murder mystery novels to kill people. Stay the heck away from it, because the fumes are poisonous! Diamonds, rubies, and sapphires are minerals too! For a complete list (and a few explanations) of minerals, check out Mineral Net.
Ah, amethysts! Amythests are the purple variety of Quartz. The purple in them is caused by manganese or iron impurities in the surrounding rock while the mineral (yeah, that's right, amythest is a mineral!) forms. Chemical compound: SiO2 (silicon and oxygen). Amythest is a weird little mineral. It has a tendency to form in volcanic pipes (the holes in the ground that lead from a magma chamber to the surface,or another magma chamber). It also forms as geodes, which are dull-looking, round gray rocks. They look pretty boring until you cut them open (using a diamond saw), and find beautiful purple crystals on the inside! I've seen people cut them open before: you have to put the geode in a special little room with the saw, and then operate the saw by looking through a window into the little room. Sometimes, the geodes explode when you're cutting them, so no one can be in the actual room that they're being cut in. The diamond saw gets really, really hot, so you have to have another little machine squirt water on the geode while you're cutting it (otherwise, it'll be much more likely to explode, or maybe burst into flames!). Geologists don't know when they pick up the boring-looking rocks whether or not there is amythest inside of it. Some scientists have to cut open 30 to 40 rocks, that are just boring old rocks on the inside, before they find one that has crystals on the inside (these ones are called geodes). Amythests can be found in Mexico, Brazil, Uruguay, the Ural Mountains of Russia, Arizona, Colorado, Maine, Montana, and sometimes North Carolina. For more detailed info on Amythests, check out The Mineral Amythest.
The strongest earthquake ever recorded occurred on May 22, 1960, in southern Chile. It measured a whopping 9.5 on the Richter Scale (Mw), and resulted in over 2,000 deaths. It was SO BIG, in fact, that the motion of the earth in Chile set off a tsunami, which caused an additional 61 deaths in Hawaii, 138 in Japan, and 32 in the Phillipines! It also caused millions of dollars of damage, and left hundreds of thousands of people homeless. Hey, when we say earthquakes are disasters, we mean it! To find out more about how earthquakes are measured on the Richter Scale, visit Virtual Earthquake.
Neill's Geology: Seismologists
When continental glaciers formed at the beginning of the Ice Age (the Pleistocene), they expanded from the North and South Poles to cover huge portions of North and South America, Eurasia, even some parts of Africa. When temperatures rose after the Pleistocene, the glaciers receded back towards the poles.
Try Cybersoils for more information. It depends a great deal on what you are looking for, but perhaps some of the resources listed there will help you.
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