Aegirine: An Uncommon Common-Mineral

Aegirine is common, in fact it is a component in some types of rock, but good crystals are significantly rarer. These crystallize in the monoclinic system and look like tiny models of the Washington Monument. Aegirine is black, but it bears tinges of red, green or brown. Its vitreous luster gives it the shimmer that we associate with glass and quartz.
As is the case with many minerals aegirine was once known by a different name because it was not well-understood. Sweden’s famous chemist Jons Jacob Berzelius was the first to unlock the secrets of the mineral’s chemistry some time in the early 1800s. Once he had identified its chemical structure he changed the name from acmite to aegirine, naming it after the Norse sea-god Aegir. It was suggested that he name the new mineral after him self, but he refused the honor and for his humility I tip my hat to him.
As I said before aegirine is a common mineral, but collectable specimens are only found in a few places. These include: Malawi, Russia’s Kola Peninsula, Norway, Greenland, and Arkansas.
I hope that you’ve enjoyed this post about aegirine. For a mineral with no technological uses nor any applications in jewelry it is quite an interesting stone.

Marcasite: The Brother of Pyrite

Marcasite and pyrite have a great deal in common. In fact they are each composed of the same chemical! Read on and learn more about this fascinating mineral--the brother of pyrite.
Marcasite is a polymorph of the chemical iron sulfide, just like pyrite. (You can read more about polymorphs in my post Polymorphism: One Chemical Many Minerals published on this blog May 6, 2011) Marcasite is of a similar pale-yellow color and it shines with a metallic luster as does pyrite. It gets its name from the Arabic word for pyrite and jewelers still call pyrite “marcasite.”
If there are these many similarities between the two minerals then how on earth can anyone tell them apart? Well, it has been difficult. It wasn’t until the 1800s that anyone could differentiate the two. There are some characteristics that are different, though. For starters marcasite has a different crystal shape than pyrite. Pyrite crystals are cubic whereas marcasite’s are orthorhombic. Now, when its crystals twin they can look like spears. Marcasite can also form in bladed, tabular, prismatic, massive, botryoidal, nodular, and stalactitic habits as well as “cockscombs” which look like the combs on chickens’ heads. Unless a marcasite specimen has very well-formed crystals it can still be a challenge to differentiate it from pyrite. Fortunately marcasite’s streak is a little different (read more about the streak test in my Nov. 1, 2010 post Pyrite the Imposter) Marcasite’s streak is greenish brown whereas pyrite’s is greenish black. Marcasite also exhibit’s a sulfur smell, which, as far as I know, pyrite does not.
There is one property that marcasite exhibits that pyrite does not, which I find rather unfortunate. Marcasite is unstable and will decay in the air. How fast it decays depends a lot upon how pure the sample is and how it is stored and handled. I keep mine in an air-tight container with a moisture-absorber, but so far no one has found a way to keep them from decaying indefinitely.
Marcasite is found in such places as: the Czech Republic, France, Greece, Belgium, Russia, Peru, Mexico, Peru, Japan, and the U.S. states of Michigan, Oklahoma, Wisconsin, Pennsylvania, Arkansas, and Illinois.
I hope that you enjoyed today’s post about pyrite’s brother marcasite. Next time I plan to write about marcasite’s unfortunate decaying problem.

Mimetite: Poisonous Contents

I had known about mimetite for quite some time before I came to own a piece of it and even after I acquired one it was a while before I learned much about it. I hope you will enjoy today’s post, which shares what I have learned about the mineral mimetite.
I have discovered that mimetite gets its name from the Greek word for ‘imitator’ because it resembles another mineral called pyromorphite. It is formed when galena and other lead-bearing minerals are exposed to the air and alter over time, so it is not surprising that it often occurs with galena and anglesite.
My mimetite specimen is yellow, but I’ve learned that the mineral can also be brown or green in color. Perfect mimetite crystals are slender hexagonal prisms, but they are very rare. Mimetite is usually found as cauliflower-shaped crusts or growing in a botryoidal habit (masses shaped like bunches of grapes) Mimetite crystals can also be barrel-shaped in which case they are called ‘campylite’.
I have not read anything that would suggest mimetite is especially hazardous, but I would advise the collector to use caution when handling the mineral as it contains lead and arsenic in its chemical makeup.
Mimetite is found in such places as: the Czech Republic, Germany, as well as in the Mexican states of Durango, Sonora and Chihuahua. It is also found in Arizona.
I had a lot of fun learning about mimetite and I hope that you have, too!

Obsidain: GlassFrom the Volcano, Part Four: Is It a Rock or a Mineral?

For the time being I am finished talking about obsidian. For my final obsidian post I would like to answer a question that some may be wondering: is obsidian a rock or a mineral?
To be honest I’m not exactly sure. To be classified as a mineral a substance must be an in-organic, naturally occurring, homogenous solid that has a definite chemical composition and a crystal structure. A rock is a natural aggregation (mixture) of minerals. Generally a rock is a mixture of more than one mineral, but sometimes it is composed of only one such as marble, which is made entirely of calcite. Obsidian is an inorganic homogenous solid, but it has no crystal structure and an indefinite chemical formula. One piece that I read described obsidian as a mineraloid, which is a mineral-like substance that does not have a crystal structure, and is of an indefinite chemical composition. This very same piece, however, also described obsidian as an igneous rock, a label that obsidian is also able to wear as it is a mixture of minerals. Most other books that I’ve read seem to call obsidian a rock, but it is still a difficult call to make.

Obsidain--Glass From the Volcano: Part 3, Location! Location! Location!

Since obsidian is of volcanic origin it could be found wherever there is or has been volcanic activity. Some important sources are: Arizona, Utah, New Mexico, Hawaii, Oregon, Japan, Mexico, the Indonesian island of Java, Guatemala, Iceland, Ecuador, and Italy’s Lipari Islands.
Another famous source of obsidian is Yellowstone National Park in the state of Wyoming. Many scientists assume that there was a volcanic eruption there many years ago, so it makes sense that one can find obsidian there. (There is actually a large outcrop of the stone in the park called “Obsidian Cliff.”) I myself found two nice pieces of obsidian in Yellowstone when my family and I went there last year. One was a nice glassy, black, translucent chip about the size of a quarter and the other was a black, nearly opaque, broken lump with beautiful spheres of white minerals in it, one of which was exposed by a break. Unfortunately, I couldn’t add these to my collection because it is illegal to remove minerals from a national park! I was, however, able to photograph them and I’ve used the photo of the little chip as this post’s picture.
Next week I will make my final obsidian post (for now, anyway) which explores obsidian’s curious properties.

Obsidian: Glass From the Volcano--Part 2

Well, I’ve kept all of you waiting long enough to read about obsidian’s uses. Here is the long-awaited post which describes how this odd volcanic glass was used in the past and how it is used today.
Obsidian is arguably one of the most useful stones in all of Creation. Like quartz and flint, obsidian breaks with a conchoidal fracture (which means that its chips look like conch shells) Anything that breaks with a conchoidal fracture can be flaked into very sharp blades (this is called 'knapping') Obsidian is no exception. In fact, obsidian has the sharpest cutting edge of any natural material! In the past people have used obsidian to make such bladed tools as arrowheads, knife blades, spear heads, saws, and axe heads. Obsidian is actually still used to make these implements by hobbyists (my self included) and for use in ocular and neurosurgeries. The reason that obsidian is used in surgery is because of the fact that it can be given a finer edge than stainless steel and therefore it leaves finer cuts that heal faster and leave less scar tissue behind.
Obsidian has been used to make jewelry for thousands of years and is still polished and cut for this purpose today. Another use for obsidian that is no longer around today, but nevertheless still fascinating is as a material for making mirrors. This was done by the Aztecs and the people of Ancient Greece. I’m not exactly sure how they made mirrors out of obsidian, but I do find the idea an intriguing one!
I hope you enjoyed today’s belated post. The next will discuss the locations in which obsidian is found.

I'm Back

Hello everyone. It's been more than a year since my last post and for that I appologize. A lot of other things have come up and I let this slide onto the backburner. I will be adding more interesting things in the near future!