The building blocks of rocks

Today I want to talk about my first love, rocks.
I studied rocks for three years. I got to see rocks, hold rocks, scratch rocks, memorise rocks. Sometimes I got to go on field trips and look at really, really big rocks.

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Rocks are pretty great.

What’s also pretty great are the building blocks of rocks, minerals. 
Minerals are the natural crystalline structures found within rocks, and are used to interpret what kind of rock you’re looking at e.g. garnet, topaz, diamond.  They are solid structures made up of chemical bonds and there are around 4000 different kinds identified so far. Although it’s not generally the best way to identify a mineral as most minerals are white in their purest form, the colours of minerals can also be pretty exciting and draw people in. 

minerals

We learnt about wavelengths waaay back here and it’s the amount of absorption of these wavelengths which determines the colour of a mineral.

It is mostly atomic bonds within these minerals which do all the wavelength-absorbing.

Minerals consist of elements. For example, an extremely common mineral, quartz, has chemical composition SiO2 meaning it is composed of elements silicon (Si) and oxygen (O) bonded together.

LAtticestructure

A few elements contain electrons that like to absorb wavelengths as it is these wavelengths which provide them with a booster of energy – the amount of energy depends on which wavelength is absorbed. Bonding between different elements changes the amount of energy electrons have resulting in different colours. elements

Elements that can do this can have great influence over the colour of a mineral, even just the tiniest trace. It is also thought that almost any element could produce almost any colour.

Nickel (Ni) for example will taint minerals green as seen in annabergite

Uranium (U) will colour minerals yellow like in zippeite

Cobalt (Co) creates the violet/red colour in erythrite

Diagnosing a rock over the colours of the minerals can be pretty inaccurate. A more reliable test is that of streak. Finding the streak, or ‘powder colour’ of a mineral involves rubbing the mineral across a white, unglazed porcelain plate. The colour of the powder left on the plate is the streak. Up to 20% of minerals have streaks that are super useful in determining what mineral they are.

We can also describe rocks as mafic or felsic.
Mafic is the term used for rocks and minerals with high iron and magnesium content and generally give rocks a dark colour.
Felsic is used for rocks and minerals with high silica content and are generally light coloured. 

I loved my rocksstudies of rocks as they seem to have a story. Once you learnt the tricks, you can start to decipher the mysteries of what has happened to that rock. 
Finding diamonds in a rock tell you that it has been buried over 150km deep as diamonds only form under extremely high pressure. 
Finding halite (rock salt) is a indication of evaporation of fluid, possibly old brine lakes or seas. 

Next time you’re walking along a beach, have a little squizz at the rocks you see. If you look really close, you might be able to see little shiny different-coloured crystals of all sorts of different minerals which could end up telling you a really good story. 

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Karma karma karma chameleon

Today I watched an epic documentary about reptiles & amphibians. 
While watching said documentary, absorbing all the glorious David Attenborough narrations, all of the unbelievably epic shots and marvelling at a whole bunch of cold-blooded creatures, I saw the panther chameleon. 

Edging along a branch through the Madagascan forest, I was captivated. It’s pincer-like hands gripped around the branch as it crawled along, it’s individually rotating eyes looking 360° around itself. It looked so perfectly adapted to its environment, I was in awe. 

And then I realised.

Chameleons are colourful. 

My blog is about colours. 

I can write all about chameleons! 

I’m sure this will surprise you all when I say I’ve never really known a lot about chameleons or any sort of reptile for that matter, so we’ll be starting with the basics. 

Chameleon

CHAMELEON

  • A chameleon is a type of lizard, part of the suborder Iguania
  • With 171 different chameleon species, the majority of them are found in Madagascar 
  • The largest chameleons are over half a metre long (69.5cm)
  • The smallest chameleons can be only 16mm
  • The chameleon will continuously grow throughout it’s life
  • Chameleons eat insects and birds with an absolutely crazy tongue that can shoot out twice as far as its body length
  • They are 1 of only a small number of animals that can change the colour of their skin

Now this is where it gets interesting. It’s a common assumption that chameleons can just change their colour to match their surroundings. Scientists believed they changed colour in the same way that octopus or squid do by adjusting pigments in their skin cells to alter colours. 

However, it doesn’t work quite like that. 

Chameleons change the colour of their chameleoncellskin in response to their emotions or environmental factors like light or temperature. More recent research has discovered they do it by changing the actual structure of their uppermost layer of skin cells called iridophores. 

These iridophores contain nano-crystals (made up of guanine, one of the key components of DNA) which will determine the colour of Chameleons skin. 
When these nano-crystals are all close together, the chameleon is in a relaxed state. Because of this closeness, only small wavelengths such as blue or green are reflected from the cells and that is the colour we see the chameleon as. (To read about different wavelengths of colours click here).

When a chameleon gets amped up, say if a rival comes along, the chameleon will stretch his skin. This spreads these nano-crystals apart from each other and will consequently reflect colours of longer wavelengths such as yellow, orange and red


Beneath this fascinating upper layer of cells is another, thicker layer of skin cells. Scientists believe it is this secondary layer of cells which help to maintain the temperature of the chameleon as the cells found here reflect near-infrared sunlight. 

However, all this cool skin cell stuff going on, only really happens in male chameleons. Female and babies are generally dull colours as they don’t need to be competing with rival chameleons therefore their upper layer of iridophores is greatly reduced in comparison.

To conclude one of my favourite blogs to write so far, chameleons are pretty amazing creatures. For more interesting info on chameleons check out these resources: