The Six Most Awesome Rock Minerals (For Various Reasons) Part 2

The Naica Mine in Chihuahua, Mexico, is home to some of the largest selenite crystals (a variety of gypsum) in the world.

Welcome to the second instalment of this two-part blog series on the six most awesome rock minerals (for various reasons and in no particular order.) In the first instalment, we looked at iron pyrite for its wonderfully geometric crystals and diamond for its many different traits, not least of all its hardness and beauty. Lastly, the limelight was cast on fluorspar for its property of thermoluminescence, which is science speak for “going disco when thrown into a camp fire.”

We have three most awesome minerals yet to examine, but before I get cracking, I need to state that this selection doesn’t even scratch the surface of the sheer diversity of rock minerals, crystals and gems that are forged within the hot and pressurized interior of our planet. There are really so many rock minerals that are awesome:

  • Mica forms incredible flat sheets of translucent monoclinic crystals.
  • Amethyst derives its name from its ancient medicinal use as protection against poisoning and drunkenness (look how that turned out for the ancient Romans).
  • Calcite is special because it double refracts light and its crystals are perfectly-shaped 3D parallelograms.
  • Halite is special because it actually tastes like salt (formed from sodium chloride) and, if left undisturbed for many, many years, can form giant columns of glittering crystals, as we saw in that picture of the Chandelier Ballroom.
  • Corundum is awesome because it’s the second hardest substance on the planet and – contrary to its ‘tough as nails’ character – is formed in cute little pink hexagonal tubes. Like miniature pool noodles.

Then, there are all those minerals and elements we covet as rare, beautiful and valuable. My choice has been restricted to those that – while commonly found (as many of them are) – are still very special and frequently overlooked. The ones I have selected here are but a mere sampling, which has been done subjectively. Why? Because science. Oh and also; this is my blog and I’m the boss.

So… with that administration out the way, let’s don our hard hats, grab our picks and get excavating!

4. Obsidian

Chemical Composition: Silicon, magnesium, iron and oxygen
Why it makes this list: Its formation process is rad
Name Origin: “Obsius” after the Roman who apparently discovered this rock in Ethiopia.
Star Sign: Haha, just kidding!

Obsidian is a jet black stone with a vitreous (glassy) lustre. Just like glass, obsidian tends to shatter into sharp fragments when hit hard, although it is much stronger than the glass your beer bottle is made of, so smashing it against your head wouldn’t be advisable. Unless you’re the kind of person who would actually smash a beer bottle against your head, in which case: knock yourself out. Literally.

Obsidian’s strength and brittleness have resulted in its use as sharp cutting implements and weapons (spear and arrowheads), some of which date back as many as six million years. Ancient Egyptians found obsidian to offer a suitable artistic representation of the iris. As such, they would use it together with a variety of other coloured gemstones to recreate their dead or dying* pharaoh’s countenance on the front of their solid gold sarcophagi.

* Pharaohs spent more time, resources and effort planning their death than they did anything else. They believed that one’s mortal life was but mere preparation for the afterlife. Millions of years later – post science and technology – the majority of the world’s population still believes exactly the same thing.

King Tutankhamen was a tenderly young Egyptian pharaoh (he was 9 or 10 when he became king) who ruled during the 18th dynasty (1332 BC – 1323 BC). This mask was used to cover his mummified remains and contains inlays of, amongst other gemstones, serpentine, lapis lazuli, malachite, garnet and obsidian.

Uses aside, what I find to be most special about obsidian is the way it is formed and it is here that we encounter a very interesting geological pearl of wisdom. The longer magma or molten rock is allowed to cool for, the larger the crystal size of the resultant igneous rock. Makes sense doesn’t it? On the one end of the spectrum, we have granite, which is formed from the ultra slow cooling of magma over many millions of years. The next time you’re bonking your partner on the kitchen counter, take a brief look at the size of the crystals within its polished surface. Big, huh? Well, incidentally, so is the size of the crystals.

In this picture, we can quite easily discern between the three composite rock minerals that make up granite. The pink crystals are feldspar, the white ones are quartzite and the black is mica. Thanks ,Science Photo Library! You’ve just facilitated the education of those who don’t have granite kitchen counters to bonk on.

At the other end of the spectrum, magma that is shock-cooled doesn’t have any time to form crystals and the resultant rock is an amorphous lump of dark brittle glass. So, essentially, what you have just learned is that granite (as we can see in the above picture) is composed of exactly the same material as obsidian (as we can see in the picture below.) Yet they look completely different! It’s like that one Kardashian sister.

So… how can you shock-cool magma? The usual method employed by Mother Nature is ejecting it at a few hundred kilometres an hour out of an erupting volcano, at which stage it theoretically becomes known as lava. The molten rock cools from approximately 1000°C (1800°F) to a little over ambient air temperature in a matter of minutes. The result is obsidian.

The truth is, obsidian is not strictly speaking a rock mineral, just as granite cannot be considered a rock mineral. Remember our Spice Girl analogy in part 1? Well obsidian is a complex blend of all the rock minerals that make up granite (feldspar, quartz and mica). As such, obsidian is more correctly termed a “mineraloid.” If I was submitting this blog to my geology lecturer for marks, I would be penalized for lumping obsidian in the same category as iron pyrite, which is a true mineral. Then again, I would have long ago flunked that paper thanks to that terrible Spice Girl analogy…

5. Opal

Chemical Composition: Silicon, oxygen and good old H20.                                      Why it makes this list: Cos it’s so damn beautiful.                                                   Name Origin: From the Latin word opalus: “to see a change of colour”

If I was a Neanderthal (my mother will argue that I am) and you placed an uncut diamond and a stone of opal in front of me and asked me to choose one based solely upon its aesthetic appeal, I would point at the opal and say: “ug.”

You may snigger at my seemingly ignorant selection, but in addition to its superior aesthetics, high quality opal fetches as much as $20,000 a carat (about R80,000). This, my friends, beats the Chuck Norris of gem stones by a fair margin.

If you have ever closely scrutinized a piece of opal, you will know just how special it is and how very hard it is to explain its unique brand of beauty. Opal is composed of tiny spheres of silica (sand, essentially) which are packed into tight water-bound layers. Water does all sorts of strange things to light. Combine that with the near-translucent silica spheres and the incoming light gets so damn confused that is splits into all seven of its personalities. These bounce back and forth between the layers and eventually exit the stone to be perceived by our eyes. The larger the size of the silica spheres, the more colours we see, while smaller silica spheres tend to refract darker blues and violet.

I could bumble on about opal, but the truth is, this amorphous gem stone is just so pretty, only a picture could do it true justice:

Is it a kaleidoscope? Is it a laser light show? Am I on acid? No! It’s opal!

 6. Magnetite

Sorry, let’s try that again.

Chemical Composition: Iron and oxygen
Why it makes this list: It’s bipolar.
Name Origin: From the name of a Greek shepherd, Magnes, who discovered magnetite on Mount Ida when he noticed his metal-tipped staff sticking stubbornly to the ground under his feet.

We tend to think of magnets as man-made things, when in fact nature is simply bursting at the seams with examples of bi-polar oddities (we all know one). Magnetite, as its name suggests, is a black metallic rock mineral composed predominantly of iron and it is the most magnetic of all the naturally occurring rock minerals on our planet. Geologists frequently keep a lump of magnetite on their desks as a paper clip dispenser.

Magnetite does, of course, have greater claims to fame: its various properties provide scientists with an insight into fancy-sounding things such as plate tectonics, paleomagnetism and magnetohydrodynamics. I have chosen magnetite for this list because it blows my mind that a seemingly unremarkable rock dug up from the ground can make metal move of its own accord. Of course, it’s not really moving of its own accord, but everyone fantasizes about having telekinetic powers every now and then. Even if the object you’re manipulating is a paper clip.

Magneto, eat your heart out!

 Class Dismissed: Your Take-Home Message

There’s really only one message I want you to take home from today’s sciencey musings. And that is that even the merest glimpse beneath the surface of any scientific discipline reveals a fathomless volume of absolutely fascinating information about the world around us and, in the context of this article, beneath our feet. Every single gem stone scattered on the floor of Scratch Patch is special for many reasons that extend beyond their appearances, just like every single human being is. Unless you’re Paris Hilton.

Now, THAT’S hot.

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 and 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 GEO101 at university – there are some that have remained firmly lodged in my memory, just like pyroclasts in a volcanic breccia (geology metaphor FTW!) 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 to 30-something year old females 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!

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 (or cubic as the geologists would say.) 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 – what else – 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 still be famous.

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 like it cut. Their diamonds too.

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 decayed teeth and so are square-cut or pear-shaped, these rocks don’t lose their shape DIAAAAMOOOOOONDS… *ahem*

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 man, 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!)

3. Fluorspar

AKA: Fluorite                                                                                                        Chemical Composition: Calcium and Fluorine                                                          Why it makes this list: For its, like, totally insane property, ‘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 partier 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 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 in the first place. 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.

This is of course just an analogy. Don’t you dare write that down in your chemistry examination.

Coming on Monday: PART 2  

You may be bored at work, but you still have to do some, you know, work every now and then. To accommodate this, I have taken the liberty of dividing this post in two. Stay tuned for the second instalment on Monday 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…

The Chandelier Ballroom: A name deserved of this cavern, which can be found in the breath-taking Lechuguilla cave complex in New Mexico. Giant otherworldly fingers of glittering gypsum crystal formations reach down from the cave ceiling.

How to Bake a Diamond

Diamonds have been getting men out of trouble for hundreds of years. They have also been getting men into trouble for hundreds of years. So, what’s so special about diamonds? They’re really pretty. They’re really strong. They have a great pair of tits.

Sorry, that’s Lara Croft.

DIAMONDS are really pretty, they’re really strong and they’re really RARE. They are also the gemstone of choice when it comes to getting hitched because, just like Shirley Bassey sang, diamonds are forever.

Diamonds are Forever… No, Really! They Are!

Aside from their unparalleled resilience and durability, diamonds are spectacular-looking rock minerals. Cut into a complex and intricate array of facets and planes, their refractive light properties send out a kaleidoscope of colour which spans the visible light spectrum, even though the gem itself appears totally translucent and colourless.

What are diamonds? What are they made of? How are they formed?

Yeah, yeah… what you REALLY want to know is what it takes to bake your own diamond so that you can become super rich and super lazy just like Paris Hilton. Well, just like everything else on this planet and in our universe really, diamonds are made of tiny, tiny building blocks. A closer look into their crystal structure tells us just how these highly coveted stones are formed.

Diamond, which is derived from the ancient Greek word adámas, meaning ‘unbreakable,’ is made from one of the most common elements here on planet Earth. It’s in the soil we walk on, in the air we breathe and in the food we eat. Here’s another clue: you’re made from it.

Carbon!

The same black crap the graphite in your pencil is made of.

The same black crap your science teacher created from burning sugar.

Oh, how unromantic! Surely such a rare and highly prized stone would be constructed from something equally as exotic and just as rare? Alas, my friends. It is not the building blocks of diamonds that make these stones so special, but rather the conditions under which they are forged. It’s like baking a cake… at the right temperature and with the right cooking time, the cake will come out beautiful, spongy, moist and delicious. At the wrong temperature and cooking time, the same batter will come out black, bitter, inedible and as a totally viable bludgeoning weapon.

Carbon + Contaminant = Colour!

We’ve established that diamonds are made from carbon. Actually, they’re made from a carbon allotrope, just so that you geology geeks don’t get a kick out of correcting me. But for all intents and purposes, diamonds are essentially made out of carbon. And carbon is abundant. So, theoretically, you should be able to make your own diamonds! Just don’t tell anybody about it or you could throw a major spanner in the traditional works and symbolism of marriage, just like those pesky homosexuals who want equal rights. I mean, who do they think they are?

Hold on a minute! All it takes is carbon? Then what gives some diamonds their colour? Well noted, my avaricious rapscallions! Diamonds don’t ONLY come as colourless, expensive globules of carbon. Interestingly enough, the unique and very rigid arrangement of carbon atoms in the crystal structure of a diamond (cubic to be exact) makes it difficult for other chemical elements to infiltrate it, causing impurities. This explains why the insides of most diamonds look so beautifully pure and translucent.

Most, but not all.

Diamonds, actually, are quite snobby. They only allow very particular elements into their crystal lattice and then again, they only do this on the rare occasion. To give you an idea of just how fussy diamonds are, it is estimated that for every million atoms of well-behaved carbon, there is a single alien atom infiltrator. The result: a fantastic analogy for opening your heart to different races, creeds, genders and nationalities.

And colour!

The colour of a diamond can have a huge influence on the amount wealthy housewives get their husbands to pay for them. Blues and greens are exceptionally rare, so they will fetch a high price. Yellows and browns are more common. And there’s nothing like a brown diamond to make you feel REAL special.

Now, gather your cooking implements and turn the oven on… HOT

Diamond Recipe

 What You’ll Need:

  1. Carbon
  2. A choice of chemical impurity or radioactive element (for colour)*
  3. Titanium metal
  4. A shovel
  5. Patience
  6. A degree in town-planning

* If you want to bake a blue diamond like the one Rose threw into the ocean at the end, you need to add boron to your mix of carbon. If you want to bake a yellow diamond, you’ll need nitrogen. If you want your diamond to turn a more exotic shade of purple, pink, red or orange, then make sure you bury it close to a radioactive element, such as plutonium or uranium. Other colours, such as black, brown and sometimes even red and pink are caused by structural flaws that harbour dark impurities that only make them appear the colour they are.

Step 1: Take carbon and mix in desired chemical impurity, or pilfer local science laboratory for radioactive element.

Step 2: Put ingredients into an air-tight and incredibly durable box.

Step 3: Phone NASA for left-over titanium to build said box. If you struggle to get past some power-tripping secretary, you can always melt down your brother’s professional tennis racquet; a legacy from the days he actually thought he’d be a professional at anything. If THAT fails, dental implants are made from titanium, but whatever you do, don’t get caught at the morgue.

Step 4: Bury carbon-filled box at a depth of between 140 and 190 kilometres, or 85 to 120 miles, where there exist conditions of immense pressure and temperature. An ambient temperature of at least 1,050 deg Celsius is what you’re aiming for.

Step 5: Bake for at least one billion years, but it could take as long as three billion years. This is where patience comes in handy.

Step 6: Wait for a super-deep volcanic eruption to bring the box of crystallized carbon to the near-surface of the Earth.

Step 7: Plant a flag at the location, build a town, exploit the native inhabitants as your labour force and dig a big hole in the ground to retrieve your creation.

Step 8: Allow to cool before eating.

Class Dismissed: Your Take-Home Message

It’s probably better to buy a diamond than make your own.

This aside, the next time you walk past a jewellery store or stare lovingly at your own engagement/wedding ring, you should look, really look, at the diamond. Know that the real beauty of these radiant gems transcends the price tag affixed to them. Diamonds are half as old as the Earth. They will last your lifetime and thousands more like yours. And they’re composed of carbon; the very same building blocks that make up you and me.

The very same material that is forged in the hearts of dying stars.