All About Minerals

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Rocks are the solid material making up the surface of the Earth.

Minerals are the solid chemical compunds of which Rocks are made.

Minerals

Mindat.org is a cooperative effort by mineralogists around the world to organize in one place as much mineralogical information as possible for all to use, and is a very useful resource for beginner and expert alike.  It’s worth taking the time to browse.
  Mindat.org currently lists 5,639 different known terrestrial minerals, all made from various combinations of 92 naturally-occurring elements, (as cited in most textbooks).  Just as we learned about Rocks in the previous section, different minerals also form under different conditions, subject to the availability of constituent elements in the immediate environment, which is why some species are much rarer than others, and can’t be found just anywhere, but only where conditions were just right. 

Check out this video: A Brief Introduction to Minerals  (10:21)

Who doesn’t love a good treasure hunt?

• A video about How to Identity  the most common Rock-Forming Minerals (16:03)

You can usually identify most common minerals with some fun detective work and by applying the process of elimination.  If you know where your sample came from, first look up that location at mindat.org and scroll through the photo gallery to see if any of the specimens depicted resemble your find.
  If you can’t match it with any shown there, start off with the list of mineral species known to be found at that location.  As you obtain your test results, (your clues!) you can narrow down the possibilities to a likely candidate.  Usually an experienced collector, mineral dealer or mine owner can help you nail it down, but it’s fun to figure out on your own. 
Here’s How.

Here follows a list of distinguishing physical properties of minerals

•  Color: Note the color. It is often the first thing you notice about a mineral, and it’s a good place to start, but you might be surprised how many different colors of Microcline Feldspar, for instance, can be found within the confines of a single quarry, or masquerade as other species, such as Beryl! Besides color, note whether the specimen is opaque, translucent, or transparent.

•  Streak: Sometimes a mineral displays a different color when reduced to finely powdered form, and this can be diagnostic.  This video shows How to Use a Streak Plate.  (1:17)   You can also use the unglazed backside of a ceramic tile, or, in the field, scratch your sample against a harder object.

•  Luster: Pay attention to how the surface of your sample reflects light. This mineral feature is descriptive, more than anything elseThis video explains it very well.  (6:45)

•  Hardness: The Hardness of a mineral has nothing to do with how it feels to get clunked in the head by it, but with how scratchable it is.  This video explains how to apply this important mineral identification method.   (5:55)   The results describe the hardness relative to readily obtainable objects, and gives you a Hardness range, but in each mineral description on MIndat.org the Hardness will be accorded a numerical value, from the Mohs Hardness Scale, for reference, then you can see which minerals fall within the range you determined.

•  Specific Gravity: When collecting in the field, you will sometimes notice that a specimen feels either lighter or heavier in the hand than you would expect for its size.  Specific Gravity is how we quantify that ‘heftiness’, and this video shows you How to Measure it(1:47) In general, the heftier a mineral is, the further down the Periodic Table its component elements are, and the rarer and more collectible it is, so it’s worth checking out.   

•  Magnetism: Is the specimen attracted to a magnet?

•  Cleavage/Fracture: Another important diagnostic feature is to note the appearance of the sample’s broken surfaces. This video demonstrates how they vary and are described.  (4:29)

•  Crystal System: When a mineral forms under favorable circumstances, its internal molecular structure will dictate the crystal into which it grows. If you find a piece that appears to have a regular shape, you will need to note how many sides the shape has, and the angles at which the sides meet.  This video does a good job of explaining the first 5 of the 7 crystal systems.  (4:36)  All seven crystal systems, plus their more complex variations are explored in This Article.

•  Crystal Habits: In addition to the basic crystal structures, you may find more complex formations defined in terms of what are known as their Crystal Habits. (article)

 Fluorescence: Here’s a fun physical property of some minerals, but in most cases you will require specialized equipment to observe it. Here is a video of Fluorite from England , (1:00), which is so sensitive to the UV rays in ordinary daylight that it will fluoresce a bright blue when you take it outside into the sunshine – no equipment required!  This video is a basic lesson about Fluorescence. (1:38) There are 5 different ways Fluorescent minerals glow, as seen in This Video. (10:17)  Other cool visual effects include Phosphorescence – when a mineral keeps glowing after the UV light source is removed Tenebrescence – the ability of a mineral to change color when exposed to light, (used in self-adjusting sunglasses), and  Triboluminescence – when light is emitted due to impact or friction. 

Some mineral enthusiats focus entirely on the collecting of Fluorescent Minerals.

Radioactivity: This is another measurable physical characteristic which calls for specialized equipment to detect, but it’s good to know when extra care is needed in the handling and display of a specimen.   Here is a List of Radioactive Minerals which can be found in Nature – for the most part those which contain Uranium, Thorium, or Potassium in their composition.

•   How to Identify Minerals (22:32)

The better you get at observing and describing the mineral you found in terms of its physical properties, the more easily you will navigate the process of elimination and arrive at an answer.  Over time, as you collect, you will develop ‘an eye’ for these properties and be able to identify your specimens with confidence.

For Further Study:

•   Free Mineralogy eBooks and downloads

•   Downloads at Mindat.org

•   Final Report on the Geology and Mineralogy of the State of New Hampshire:

With Contributions Toward the Improvement of Agriculture and Metallurgy, 1884