Kyanite: the Multi-hardness Mineral

     Kyanite, which is also called “cyanite,” “rhaeticite” and “disthene” is a polymorph of a chemical called aluminum silicate. In my post about polymorphs I mentioned that I had a few polymorphous minerals to blog about and now I’ve finally gotten around to it. Pure kyanite is colorless, but most kyanite is sky blue. In fact, the name “kyanite” comes from the Greek word kyanos, which means “blue.” This common blue color comes from impurities such as iron and chromium. Other impurities produce such colors as: orange, brown, gray, pink, yellow, and green and sometimes they display color zoning. Kyanite’s crystals are long and flat and they have sharp edges. Kyanite actually has two different levels of hardness on the Mohs’ Scale. A mineral measuring only a 5 on the Mohs’ Scale will scratch a kyanite crystal if taken from top to bottom, but it will take a mineral measuring 7 or above to scratch it when taken from side to side!
     Kyanite is used to make things like fire brick, brake pads and electrical porcelains for cars, floor and wall tiles, and molds for metal casting. Kyanite is also used as a gemstone. The mineral is found all over the world, but some of the best sources are: Kenya, Zimbabwe, Tanzania, Russia, Switzerland, Ukraine, Brazil, India, the Canadian provinces of Quebec and Manitoba, and much of the United States’ Appalachian Region.
     Kyanite is somewhat or a rarity among minerals. Not because it can’t be found in many places, it’s quite common in that way. No, kyanite is rare because of its properties. After all how many other minerals have different harness values depending on the direction that you scratch them?

Wolfram: an Inventive Mineral Name

     As I was doing some research for my post about hubnerite I came across some information about wolfram. Wolfram is not actually a mineral, but rather a name that was once applied to two different minerals when both were thought to be the same (you can read a little more about this in May 19th’s post Hubnerite: Black Beauty) Despite the fact that wolfram is actually two minerals I would still like to write about it today simply because of the origin of its name. In my post about mineral names I told you that a mineral’s name is often just a description of its properties in another language, usually Latin or Greek. This is the case with the word “wolfram,” but the language used to describe its interesting properties is actually German.
     There is a fascinating story behind the name “wolfram.” About five hundred years ago some tin miners in Germany noticed that some of the rocks that they were smelting with the tin ore caused a nasty froth to form on top of the molten metal, which destroyed some of the tin. They named the stone volfram which is composed of the German words volf which means “wolf” and rahm which means “cream” or “froth,” because of the fact that this cream “devoured the tin like a wolf.”
     During the time that I have spent learning about minerals and their names I have seen names translated to mean things like “cross stone,” “golden leek,” and even “the stone that leafs apart,” but I think that “wolf cream” is the most inventive one that I’ve ever seen!
     P.S. tungsten also used to be called wolfram (this likely has something to do with the fact that tungsten is found in the stone) and it is still known by this name in some countries. That is why tungsten is a W on the periodic table.

Hubnerite: Black Beauty

     Hubnerite is a black mineral whose crystals are flat rectangular prisms. Most of the examples that I’ve seen have front and back faces that are nearly perfect squares, but I’ve also seen a few that are more stretched out. Despite the way that I described it above, hubnerite is not always black. Actually pure hubnerite is reddish-brown or red and is translucent or transparent, but iron impurities can cause it to become black and lessen its translucency until it actually becomes opaque. Other impurities can give rise to other colors in hubnerite such as brownish-black, brownish-yellow, and brown. At one time hubnerite and another mineral called ferberite were thought to be the same mineral (this mineral’s name was wolfram.) Eventually scientists realized that the two were not the same mineral, but just very similar. Ferberite is composed of a chemical called iron tungstate and hubnerite is composed of manganese tungstate.
     Hubnerite is used as an ore of the metal tungsten. Tungsten is used to make steel alloys, the filaments in some incandescent light bulbs, and welding electrodes (the acronym TIG in TIG welding stands for “tungsten inert gas.”) Tungsten is also used to make a chemical called tungsten carbide, which is also known as “hardmetal.” True to its name hardmetal is very hard. I have used a knife sharpener that is made of hardmetal and have personally watched it peel stainless steel like a carrot! Hardmetal is also used to make scratch-resistant rings.
     Hubnerite is found in such places as: Peru, Mexico, Romania, Japan, Bolivia, Sweden, South Dakota, Washington state, North Carolina, New Jersey, and much of the Western U.S. Hubnerite has a place on my list of favorite minerals simply because of its unusual color and the fact that it contains tungsten, which few other minerals do!

An Adventure In Mineral Names (Maybe They do Mean Something Afterall...)

     Let’s be honest, there are a lot of mineral names out there that just don’t make sense. Sometimes it seems like there’s no rhyme or reason to them and that the scientists just wanted to make up the goofiest names possible! Actually the minerals’ names (even the odd ones) do have some meaning behind them. That is what I’d like to explore today.
     Minerals are usually named for something. After all, it is much easier to base a name on something than to simply invent one out of thin air. A lot of minerals are given a name that describes something about them in another language, Latin and Greek being the popular languages to use for this purpose. For example: the mineral scolecite gets its name from the Greek word skolex, which means worm. Scolecite was given this name because it has a tendency to curl like a worm when it’s heated or dehydrated. The second most popular thing to name a mineral after is the proper name of a person or place like ulexite (which is named for the German scientist George L. Ulex) and aragonite (which is named for Aragon, Spain.) Some minerals are named for the elements that make them up like molybdenite and vanadanite, which are named for the elements molybdenum and vanadium respectively, but these sort of names are rare in the mineral world.
     What about the “normal” mineral names? It would appear that most of these minerals were discovered before modern science came about and that the names are simply ancient words for the stones.
     I hope that you’ve had fun learning about the origins of mineral names and I hope that these names don’t seem quite so strange now!

Polymorphism: One Chemical, Multiple Minerals.

     I have a few minerals that I’d like to blog about in the future that are polymorphs, so I figured that it would be a good idea to post a blog about polymorphs first. Polymorphs are simply minerals that have the same chemical makeup, but different crystal structures. For example, the chemical titanium dioxide can actually form three different minerals: brookite, rutile, and anatase. Rutile has prismatic tetragonal crystals, anatase has tabular (flat) tetragonal crystals, and brookite has orthorhombic crystals, yet all three are the same chemical. The chemical makeup of a mineral (its molecules) can determine a great deal concerning the mineral's properties, but the way in which these molecules are arranged when the substance crystalizes can also affect them as well. Think of it this way: if you have three red Lego blocks and four blue ones you can build any number of different objects with them, yet they are the same three reds and four blues. The same thing is happening in polymorphism: one type of molecule might usually arrange itself in one way, giving the crystal certain properties; but it can also arrange itself in another way, giving the mineral a whole new range of properties.
 How does this happen? The way that the chemicals that make up polymorphous minerals crystallize depends a lot on their surroundings. Heat and pressure have a lot to do with what polymorph is formed (by the way, the term “polymorph” also refers to each form of the chemical. For example calcite and aragonite are both polymorphs of calcium carbonate.) There is a great deal more science that could be delved into here, but for now I’ll leave it out.
     Sometimes certain polymorphs of the same chemical are less stable than the other. Anatase and brookite both become rutile when subjected to intense heat, and aragonite will slowly revert to calcite over time and will do so rapidly when heated.
     I hope that the subject of polymorphism in minerals was as interesting to you as it was to me. I also hope to make some posts about a few polymorphous minerals soon!