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Mineral Monday: Bismuth By Request

Bismuth_crystal_macro

By popular request (ok, by Rose’s request,) today’s Mineral Monday is bismuth!

Bismuth is element number 83 on the periodic table, and there are so many weird facts about it, I really have no idea where to start.

No, that’s a lie, I do.

Let’s begin with a French chemist named Claude François Geoffroy. Geoffroy, who came from a family of apothecaries and other scientists demonstrated that Bismuth was not the same thing as lead in 1753.  He died that same year. Poor guy.

Looking at the above picture, it’s kind of easy to make light of Geoffroy’s achievement. I mean, that doesn’t look anything like lead, right? But out in the real world bismuth doesn’t look like a tie-dyed M.C. Escher painting. In fact, it usually doesn’t even occur in visible crystals, and usually you can find it in ore, where it looks like this:

Bismite, an ore of bismuth. Image Credit: Wikimedia Commons

Bismite, an ore of bismuth. Image Credit: Wikimedia Commons

I know, I know. It’s not nearly as pretty. In order to get the pretty, specimen-worthy versions, pure bismuth is down and grown in labs, to get insane crystals. Technically, because these specimens are lab grown, they aren’t minerals (minerals have to be naturally occurring,) but really, who cares? It’s amazing. Bismuth technically can form crystals in nature, but it’s usually so mixed-in with other materials (like lead) that it never really gets the chance to grow to it’s full potential. And what a potential it is.

Bismuth crystals on right, and bismuth metal on left. Which one do you want? Image credit: Wikimedia Commons

Bismuth crystals on right, and bismuth metal on left. Which one do you want? Image credit: Wikimedia Commons

Those psychadellic colors are a result of a thin layer of oxide or tarnish that forms on the surface of the lab-grown structures.

Though it takes on beautiful shapes and colors, bismuth isn’t just a pretty face. It’s other properties are just as entrancing. Bismuth is one of the few materials that expands when it solidifies, just like water. It’s also very diamagnetic, which means that it repels magnetic fields, with dramatic results:

Bismuth is also (technically) radioactive. It has a half-life of 19,000,000,000,000,000,000 years. To put that in perspective, consider this, from an article on ChemiCool: “If precisely 100 grams of bismuth-209 had been present at the beginning of the universe 14 billion years ago, about 99.9999999 grams of it would still be around today.” Insane, right?

Ok, last crazy bismuth fact of the day. Ever wonder where the ‘bis’ in ‘Pepto-Bismol” came from? Of course not. But now you can wow your friends with the non-sequitur that bismuth (or more accurately, bismuth subsalicylate) is an active ingredient in the violently pink wonder drug. Popular Science even has an article about how to extract bismuth from Pepto-Bismol tablets.

If you’re a little more hard-core DIY and want to make your own bismuth crystals, and you have access to metalworking equipment, there are plenty of instructional videos and detailed guides out there ready to help you out.

Field Day Friday: Mammoth Cave

Mammoth Cave Tour Image Credit: Wikipedia

Mammoth Cave Tour Image Credit: Wikipedia

It’s been one of those weeks. One of those terrible, awful weeks that everyone just wants to be over and done with. One of those weeks where yes, thank you, I really would prefer to go hide in a cave somewhere rather than stay compulsively glued to the news. This week, my daydream rock-related getaway is Mammoth Cave.

Mammoth Cave, in Kentucky is the world’s longest known cave system according to the National Park Service, with around 400 miles of tunnels explored. The NPS also evocatively describes it as “A Grand, Gloomy and Peculiar Place.” That sounds about right. I’ve only been in a few caves, but the impression I had of them was that they certainly are “grand and peculiar places.” There is something sacred and beautiful about being in a cave, like being within the embrace of the earth. And I don’t know about you, but I am sorely in need of a hug this week.

Image Credit: Wikipedia

Image Credit: USGS via Wikipedia

 

Thursday Treasures: Ancient Coins at the MFA

Maronia Tetradrachma, a greek coin from Thrace featuring the god Dionysos Image Credit: Wikimedia Commons.

Maronia Tetradrachma, a greek coin from Thrace featuring the god Dionysos Image Credit: Wikimedia Commons.

The Museum of Fine Arts (MFA) in Boston is a treasure in and of itself. It is stunningly beautiful, and absolutely packed with some of the most incredible examples of art, from pre-history to the modern era. They have a new gallery of ancient coins which is apparently “the only permanent exhibition space for ancient coins in a US art museum.” It has over 500 greek and roman coins on display, a mere fraction of the 7,500 in the museum’s collection.

Coins are interesting archaeologically, not just as valuable artifacts, but also as a window into the lives of people in the past. Coins with inscriptions might be used to gauge what group or government was in power when it was minted. Coins that show up in lands far distant from their original location can help archaeologists figure out trade routes, and images of rulers allow modern historians to literally associate a face with the name of a historical figure.

Not only that, but they can give us great information about what kinds of fashion and hairstyles were favored at the time. The coin pictured above is an ancient greek coin featuring the god Dionysos with a fantastic updo-one that would probably not be all that popular among guys in Greece today.

If you can’t make it to Boston, the MFA does have an iPad app available for free which featured detailed images of the coins in the collection, as well as historical and material information for each one.

Barchans on Mars

 

Barchan Dune in Namibia Image Credit: Wikimedia Commons

Barchan Dune in Namibia Image Credit: Wikimedia Commons

Sand dunes are basically mobile piles of millions of tiny bits of rock, sculpted by the wind into fantastic shapes. One of the coolest shapes is today’s weekly geology word, barchan. The Encyclopedia Britannica has the following definition:

barchan: also spelled Barkhan,  crescent-shaped sand dune produced by the action of wind predominately from one direction. One of the commonest types of dunes, it occurs in sandy deserts all over the world. Barchans are convex facing the wind, with the horns of the crescent pointing downwind and marking the lateral advancement of the sand. These dunes are markedly asymmetrical in cross section, with a gentle slope facing toward the wind and a much steeper slope, known as the slip face, facing away from the wind. Barchans may be 9–30 m (30–100 feet) high and 370 m (1,214 feet) wide at the base measured perpendicular to the wind. They gradually migrate with the wind as a result of erosion on the windward side and deposition on the leeward side. The rate of migration ranges from about a metre to a hundred metres per year. Barchans usually occur as groups of isolated dunes and may form chains that extend across a plain in the direction of the prevailing wind.

A handy illustration of a barchan dune Image Credit: wikimedia commons

A handy illustration of a barchan dune Image Credit: wikimedia commons

How cool is that? Giant crescent-shaped dunes moving slowly across a desert or plain, pushed along by near-constant wind. Or, you know, across the surface of other planets. Barchans have been photographed making their way across the surface of Mars, with their distinctive crescent shape visible from space. Martian barchans. Awesome.

Barchan Dunes on Mars Image Credit: NASA HiRISE

Barchan Dunes on Mars Image Credit: NASA HiRISE

Another Earthquake in Iran, 600-year-old Murder Mystery, and Armor Piercing Cannonballs

 

A Scottish Crannog Photo Credit, MB Griggs

A Scottish Crannog Photo Credit, MB Griggs

Today, the news is rightfully dominated by the marathon bombings in Boston, but while we’re mourning, reading about news in other parts of the world might be a helpful distraction. Here’s your weekly round-up of rock-related news.

Geology