The 6 Most Awesome Rock Minerals (For Various Reasons), PART 1

Geology is just one of the many scientific disciplines that have fascinated me over the years. As a teenager, I became fanatical about collecting rocks, rock minerals, crystals and fossils, every specimen of which I arranged fastidiously along the wall shelf that overlooked my desk (see photo below). I am proud to say that this extensive collection has been lovingly preserved in its original arrangement by my mother, starting with translucent colourless quartzite crystals, ranging right through the colours of the rainbow and ending with opaque, jet black fragments of obsidian. Dust and the occasional long-dead beetle aside, not a single rock has been discarded. They’re all there and they’re all special. I would like to extend a thank you to my mom for preserving my collection, although it wouldn’t hurt you to dust once in a while…

My personal collection of rocks, rock minerals, crystals, coral and fossils.

Collecting Rocks is Not Just for Boring People

Why on Earth would anyone collect rocks? Well, rocks tell us about the history of the ground underneath our feet and you don’t need to be terribly nerdy to appreciate that! Unfortunately, too large a percentage of that ground has been covered in concrete, ceramic tile, plush carpets, hardwood or laminate (if you’re a cheapskate.) But beneath the man-made veneer of our planet lies a fabulous variety of rock types, minerals and crystals, each with a history, each with a unique set of properties, each comprising a piece of the puzzle that, once put together, tells the story of the formation of the Earth and how the land came to be shaped the way it is.

My deep interest in mineralogy and geology was and is about more than just the pretty appearance of certain rock minerals and crystals. It’s about their unique properties, characteristics and traits, a handful of which you will come to learn about in this two-part blog. Of the many rock minerals I have collected over the years and encountered during my University geology classes, there are some that have remained firmly lodged in my memory, just like pyroclasts in a volcanic breccia. These are the rock minerals that, in my mind, are true testaments to the sheer awesomeness of the natural world.

And the Nominees Are…

Firstly, in the interests of scientific rigor, let me stipulate the following: this list is totally subjective, so forget the part about “scientific rigor.” The facts I present, however, are true! Secondly, my choice is restricted to rock minerals or gemstones. Not rock types, such as marble, granite and shale. Minerals are the building blocks of rocks, just like desperate and marginally talented 20-something year old girls are the building blocks of girl groups.

Granite, for example, generally consists of three different rock minerals: Scary Spice, Baby Spice, Fanta Pants and one that looks like a lesbian. Hold on… I’m getting confused. That’s four spices.

Anyway, you get the point, so now that you know what a rock mineral is, let’s get to it! Get your De Beers on ‘cos we’re going digging!

Awesome Rock Mineral # 1: Iron Pyrite

AKA: Fool’s Gold

Chemical Composition: Iron and sulphur

Why it makes this list: Iron pyrite crystals are one of the most incredible demonstrations of symmetry in nature.

Name Origin: Pyrite originates from the Greek word for “fire”

We tend to think of nature as being random and chaotic, but rock crystals are a beautiful example of how there is more flawless pattern and symmetry in nature than there is entropy and disorder. Iron pyrite is one of my favourite examples, with its brassy yellow crystals that are seemingly impossibly square in shape. Pyrite frequently grows in great tangles of inter-grown geometric shapes, most commonly cubic and octahedral. The result is both incredibly beautiful and intriguing: something that could pass as the work of an abstract artist on acid.

Iron pyrite has been dubbed “fool’s gold” owing to its glistening metallic yellow colour, which makes it look quite similar to gold; one of the most coveted elements on Earth. There are many differences between pyrite and gold, of course, but the most important to mankind is that iron pyrite is appallingly common and is likely to get an icy reception from your wife or girlfriend if given as a gift.

Then again, Jessica Simpson is living proof that you can be appallingly common AND rich at the same time.

Awesome Rock Mineral # 2: Diamond

AKA: A girl’s best friend.

Chemical Composition: Carbon and sometimes trace elements

Why it makes this list: Diamond doesn’t need an excuse to make this list.

Name Origin: Diamond comes from the Greek word adamas meaning “unconquerable” or “invincible.”

Diamond is the Chuck Norris of gemstones. It’s hard, it’s tough and it’ll charm the pants off any lady. Formed deep in the Earth’s crust under conditions of bone-pulverizing pressure and temperature, diamond is the hardest known substance in existence and it wins this title by a very, very, very large margin.

When cut correctly, diamond’s reflective and refractive properties emit a kaleidoscopic disco of light, coruscating with every colour of the rainbow. Uncut, diamonds are translucent and have an almost greasy or soapy lustre; certainly not something one might describe as breathtakingly beautiful. Most ladies prefer it cut. Their diamonds too.

An uncut diamond, which just goes to show how important cut is to the aesthetic appeal of this gemstone.

In addition to their aesthetic appeal, which has been adored and worshipped by cultures and civilizations across the world for centuries, diamonds also have rather useful modern applications. Actually, 80% of all the diamonds unearthed are exploited for their incredible strength as blades, grinders, bearings and drill bits. The other 20% are considered too pretty to be used for drilling open rotten teeth and so they are square-cut and pear-shaped, these rocks don’t lose their shape DIAAAAMOOOOOONDS…

*ahem* sorry.

There are many things that make diamonds exceptionally awesome: they’re the only gemstone composed of a single element (carbon), they’re the hardest substance known to humankind, they’re incredibly beautiful and they’re incredibly expensive. But the bottom line really is that diamond’s awesomeness transcends time, culture, civilization and class. Diamond is king (and a giiiiiiiiiiiiirl’s beeeeeeeeest frieeeeeeeeeeend!)

Awesome Rock Mineral # 3: Fluorspar

AKA: Fluorite

Chemical Composition: Calcium and Fluorine

Why it makes this list: For its, like, totally insane property known as thermoluminescence.

Name Origin: “Fluo” is the Latin word for “to flow.”

I first came across Fluorspar on a seven-day canoe trip down the Orange River, which is the natural border between South Africa and Namibia. On our fourth or fifth day, the guides pulled the canoes off the river onto Namibian shores and took the younger whipper-snappier of us on a gruelling 45-minute hike up the steep, boulder-strewn slopes. At the summit, we found an old abandoned fluorspar mine. There were just piles of this translucent green and purple mineral lying everywhere. So, we all filled our pockets and headed back down towards the camp.

That night, our chief guide showed us just why fluorspar was so damn cool. Onto the searing-hot coals that were the remainder of our nightly camp fire, he cast a handful of broken fluorspar shards and dust. After a few seconds, these rocks started to glow bright electric blue and green before shattering like popcorn into smaller fragments. In spite of the burning-hot bits of shrapnel that were sent whistling past our heads, we were enraptured by the performance and I have used fluorspar to impress girls ever since.

Unfortunately, I have run out of fluorspar.

Fortunately, I have my personality to fall back on.

Fluorite is the trance party-goer of the mineral world

Fluorspar or fluorite most commonly comes in cubic crystals, although the one’s we found on the Orange River had all been shattered or broken at some stage and so ranged in amorphous size. “Fluo” is the Latin word for “to flow” and this name was given to this rock mineral for its applications in iron smelting. In a peanut shell, fluorite decreases the viscosity of molten iron, helping it to flow better.

It was only after the discovery and naming of fluorite that its awesome physical properties of fluorescence and thermoluminescence were discovered, which is incidentally where the word “fluorescence” comes from. Fluorescence – the emittance of that strange otherworldly light – is caused by the dancing of electrons within the mineral’s atomic structure. As they stomp around to the doef-doef music in their heads, they emit quanta of visible light that is most frequently blue in colour, but can be green, white, red, purple or yellow.

Stay Tuned for Part 2…

You may be bored at work, but you still have to look busy or else your boss will give you the boot. To accommodate this, I have taken the liberty of dividing this post in two. Stay tuned for the second instalment in which we shall intrepidly explore the remaining three most awesome rock minerals!

In the meantime, your homework is to ‘ooh’ and ‘aah’ at this picture…

“Lechuguilla Chandelier Ballroom” (New Mexico) by Dave Bunnell. Licensed under CC BY-SA 2.5 via Wikimedia Commons. Giant otherworldly fingers of glittering gypsum crystal formations reach down from the cave ceiling.

Sciencey LOL of the Week

Plate Tectonics: The Ends (and Beginnings) of the Earth, Part 1

Is it possible for something that’s spherical to have a physical end or beginning? A ball just keeps going on and on and on and on. No matter how many times you turn it, you never get to any definitive beginning or end. Where does an egg start and where does it end? With the chicken or the egg or the chicken or the egg or the chicken?

Well, in spite of its spherical shape, planet Earth has many beginnings and endings and they are found at the boundaries of the colossal shifting plates that comprise its surface! Plate tectonics account for many of the soaring and plummeting landscapes on our planet and it explains a host of our most frightening natural disasters, from spewing volcanoes to shuddering earthquakes. It builds beautiful fertile islands in the middle of vast ocean expanses while ripping the ocean floor apart elsewhere, forming trenches in excess of 10 kilometres deep. Understanding plate tectonics is key to understanding our planet and its dynamic surface, which, as stable as it seems under our feet, is in reality anything but. 

The Earth’s Surface is Divided into Plates

The Earth’s outermost crusty layer is known as the lithosphere (lithos meaning “stone” in Greek) and it can be likened to a giant shell that has been broken into large, rigid interlocking pieces (refer to the image below). These pieces sit upon the warmer and more malleable asthenosphere and basically bumble their time away by colliding into each other, pulling apart and rubbing against each other. They also, you know, support the entire biodiversity of planet Earth in their spare time.

Meet Planet Earth’s tectonic plates: Americans and Canadians get the North American Plate, Europeans and Asians get the Eurasian Plate and the penguins get the Antarctic Plate… EVERYONE gets a plate!

The asthenosphere, which is fluid-like and warmer and more pliable than the outer crusty lithosphere, promotes the migration of the Earth’s tectonic plates. Prodigious convention currents of heat and molten magma travel from the bowels of the planet to its surface, compelling these giant puzzle pieces to move. Just like Tree Ents from “the Lord of the Rings” and the cogs in your brain after a heavy night out, these motions are frightfully slow. Some plate boundaries, such as the Mid-Atlantic Ridge, move as fast as your fingernails grow, which is approximately 1 to 4 cm per year. Doesn’t exactly make for riveting viewing, does it?

But over time, patience wins out against the resistance of solid rock and the results are as creative as they are destructive. 

The Three Plate Boundary Types

All of the plates that make up the lithosphere are in constant motion thanks to the giant hot and moist “visco-elastic” asthenosphere upon which they sit. Hot and moist. If you’ll refer back to the map above, you’ll notice that every plate fits snugly into another, much like a giant jigsaw puzzle. Since each plate is in constant motion, one can definitely assume that it’s where they meet – at the plate boundaries – where the party’s at.

The picture below shows us the direction of motion of each of Earth’s tectonic plates. At any given time, one periphery of a plate is wrenching away from another. At the opposite end of the plate, there is a violent collision going on, while the sides are causing iniquitous mayhem as they rub lasciviously against each other. And as the more, erm, experienced will know… friction leads to all sorts of seismic events.

Map indicating the direction of motion of Earth’s tectonic plates. The red ‘teeth’ indicate where two plates are colliding, which, as we shall find out momentarily, has resulted in the formation of the magnificent Himalayan mountain range (continental collision) and Mariana’s trench (subduction zone). The first is home to the highest viewpoint on Earth (although you might kill yourself getting there) and the second, the very deepest point in Earth’s crust (although, again, you might kill yourself getting there). 

 1.    Convergent Boundaries: When Two Plates Collide

If you drove your car at the rate of fingernail growth into a brick wall, you would have no idea what would happen because you would have gotten out long ago to use the toilet and get married (probably in that order). But hypothetically speaking, in the absence of arseholes to use and arseholes to marry, you’d probably discover that nothing very much would happen in a collision between a brick wall and your car moving at the rate of fingernail growth. Why? Because you’re going too slowly!

BUT! Substitute your car with a billion tonne megalith and that brick wall would be cement dust in… oh a few million years or so!

The convergent boundaries of Earth’s plates result in the formation all sorts of interesting topographical features. Two colliding plates can either become a subduction zone (where one plate – usually the denser one – plummets beneath the other one), or it can become a collision zone. The plate boundaries that are home to continental soil tend to opt for the latter, while the plate boundaries that are home to ocean soil, the former.

Continental Collisions

The coolest example of a continental fender bender on Earth has got to be the Himalayan mountain range, which is home to the world’s highest, most hostile and most abundantly body-strewn slopes.  This formidable mountain range is the product of two continental tectonic plates (the Indian and Eurasian plate) crashing together and forcing each other to crumple and buckle into soaring mountain peaks and plummeting mountain valleys. There are more than 100 mountain peaks in the Himalayas that smash the 7,000 m (23,000 ft.) altitude mark. Mount Everest, the range’s and world’s largest mountain, comes in at 8,848 m… a staggering 29,029 ft. above sea level.

Typical and totally average view on a hike through the Himalayas

Subduction Zones

When two plates collide and the one happens to be heavier and denser than the other, it typically gets forced beneath the less dense plate. Imagine Paris Hilton gets into a fight with Natalie Portman. Who would come out on top? My vote would be on the substantially less dense (and Harvard degree-wielding) Miss Portman.

This kind of active plate boundary is known as a subduction zone and it can form deep-sea trenches that plunge for kilometres into the ocean floor, as well as yawningly vast abyssal plains that are home to a plethora of deep-sea squishies, only a fraction of which have had the pleasure of joining our taxonomy system. The remaining majority have not yet been discovered or named, although one did feature very briefly in the Pixar animated film, Finding Nemo.

 The vertical antithesis of the Himalayas is Mariana’s Trench, a deep gash in Earth’s crust in the Mid-Pacific, directly east of Southeast Asia (refer to the map above). Here, the Pacific plate smashes into the Philippine Sea Plate and the former, which is composed of denser, more metal-rich rock than the crusty, silty continental latter, gets forced downwards. There are examples of mid-ocean trenches all over the world, but at 11,000 m (36,070 ft.), Mariana’s Trench is the very deepest. Not even an inverted Mount Everest could fill this gash.

That is a huge gash. 

But wait, there’s more! One plate does not simply get sucked underneath another without the appropriate ceremony! Deep-sea trenches are very good and all, but we want fire and brimstone!

I’m so glad you asked…

The Ring of FIRE!

 When one tectonic plate plummets beneath another, it faces the fiery wrath of the Earth’s immensely pressured mantle. This heat causes the hydrous (water-containing) minerals within the plate’s rock to release their moisture. Since water acts to lower the melting temperature, the mantle overlying the subducting plate melts (surprise!), sending plumes of magma towards the Earth’s surface.

 These pockets of molten rock tend to become trapped underneath the crusty rock making up the lithosphere, where the pressure builds up. Eventually, all hell breaks loose and you get a volcanic eruption. This can occur either on the ocean floor or on land surface. Sub-aquatic volcanism tends to result in the formation of fiery, volcano-strewn islands, such as the Pacific Ring of Fire. Terrestrial volcanism tends to result in Pierce Brosnan being a hero and other awesome feats such as pyroclastic flows, earthquakes and village-bound lava lakes.

As long as the Earth’s tectonic plates are mobile, subduction will remain an ongoing process. The denser plate is continuously consumed by the continental plate, sending plume after plume of magma to the Earth’s surface, fuelling the ingoing wrath of these lithic pimples.

Stay Tuned for Part Two! 

Want to find out what happens when a billion billion tonne slab of rock rubs against another billion billion tonne slab of rock? Things get seismic.

 Stay tuned for next week’s blog instalment – Plate Tectonics: the Ends (and Beginnings) of the Earth, Part 2.