Monthly Archives: December 2015

Snowflake Obsidian – Day 25 of the Mineral Advent Calendar

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This holiday season, why not get a mineral every day instead of chocolate? Today’s mineral is Snowflake Obsidian find out more about it below..

Well that’s it for the Mineral Advent Calendar this year, I hope you enjoyed it! I finish us off today with the only snow we are likely to see in the UK today and that is Snowflake Obsidian.

Not this snowflake, that's one I made!!! Because I really wish it would snow.

Not this snowflake, that’s one I made!!! Because I really wish it would snow.

Snowflake Obsidian forms as a variety of Obsidian, which has inclusions of the mineral Cristobalite in the Obsidian. The Cristobalite forms these gorgeous white snowflake shaped growths that give rise to the name. So in a way the final mineral today is two-for-the-price-of-one! BUT Obsidian is not actually a mineral – it is a type of volcanic glass that has crystals of silica so small you can’t see them with the naked eye. We call it crypto-crystalline.

Snowflake Obsidian from Wikipedia.

Snowflake Obsidian from Wikipedia.

Obsidian:
Chemical formula: SiO2
Colour: Black to grey black
System: N/A
Hardness (Mohs): N/A
Can you find it in the UK? No

Christobalite:
Chemical formula: SiO2
Colour: Colorless, white, also blue grey, brown, grey, yellow
System: Tetragonal
Hardness (Mohs): 6 – 7
Can you find it in the UK? Yes

Whatever you are celebrating this winter season, I wish you joy!!

Whatever you are celebrating this winter season, I wish you joy!!

 

For more information about Snowflake Obsidian please visit the MinDat website.

 

Gold – Day 24 of the Mineral Advent Calendar

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This holiday season, why not get a mineral every day instead of chocolate? Today’s mineral is Gold find out more about it below..

We are coming to the end of our Mineral Advent Calendar, and if you are of Christian faith (or attended ANY school where a Nativity play was performed at Christmas) you will recognise the significance of today’s mineral as one that apparently a wise man headed out carrying to celebrate the birth of a baby – Jesus – the relious reason behind the celebration of Christmas. Though to be honest all of the new mums I know would prefer food (especially fresh veggies!) to Gold (or Frankincense or Myrrh), it’s still a great mineral for today’s advent! But whatever your religion, I hope you are enjoying the season!

Gold comes in many form but these dendritic crystals are one of my favourites. Image from Wikipedia.

Gold comes in many forms but these dendritic crystals are one of my favourites. Image from Wikipedia.

Gold:
Chemical formula: Au
Colour: Gold!
System: Isometric
Hardness (Mohs): 2½ – 3
Can you find it in the UK? Yes.

 

UK Gold (specifically Welsh) has been used in the rings of the royal family for over 80 years. Image from the Telegraph.

UK Gold (specifically Welsh) has been used in the rings of the royal family for over 80 years. Image from the Telegraph.

Gold can be found in many locations across the UK, it is a common accessory mineral to lots of other minerals mined commercially including Copper, Lead and Silver and if often found near quartz minerals. Careful not to mistake it’s more common counterpart Pyrite (or Fools Gold) which also grows in similar conditons, but it actually quite a different, more brassy colour. Famously UK gold has for over 80 years been used in the production of Royal wedding rings, including the most recent wedding between Prince William and Catherine, Duchess of Cambridge.

For more information about Gold please visit the MinDat website.

 

Halite – Day 23 of the Mineral Advent Calendar

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This holiday season, why not get a mineral every day instead of chocolate? Today’s mineral is Halite find out more about it below..

It’s December 23rd and if you have finished work and are lucky enough to have tomorrow off, you might now very be….

If so, please be safe when driving back; if the rest of the country is anything like Devon tonight the roads are pretty wet!! Fortunately (or not, depending on how much rain you get) that means we probably won’t see any of a mineral that is usually EXTREMELY common this time of year – no not Ice, but it’s related – that is rock salt, used in grit to keep the roads safe. The reason salt is used to grit roads is because it lowers the freezing point of water (meaning it has to get much colder before the water will freeze), though this only really works when the temperature is above -5 degrees. In this paper by Ari Venäläinen, researchers tried to use the mean air temperatures to gauge how much salt would be used in Finland during the winter period, but as I’m sure you can guess, the result was that although air temperatures give some guide as to how much salt people use on the roads, modelling accurate amounts was dependent on a combination of issues, including road maintenance and people’s behaviour.

Salt is most definitely a mineral, as anyone who has ever been to a salt mine can attest. Rock salt, more properly called Halite when in it’s mineral form, is something that although we may be more familiar with it on the kitchen table, is essential for safe driving at this time of year.

So stay safe on the roads if you are driving home tonight, and check out this amazing microscope image of a Halite crystal taken by Dr Natasha Stephen in Plymouth University Electron Microscopy Centre.

A lovely Halite crystal photograph taken by Dr Natasha Stephen at the Plymouth University EM centre.

A lovely Halite crystal photograph taken by Dr Natasha Stephen at the Plymouth University EM centre.

Halite:
Chemical formula: NaCl
Colour: Colourless, white, yellow, red, purple or blue
System: Isometric
Hardness (Mohs): 2½
Can you find it in the UK? Er yes! (In fact it is still mined in Cheshire)

 

Cheshire's salt mines are still very much active! Image from the BBC.

Cheshire’s salt mines are still very much active! Image from the BBC.

Halite is a common mineral all over the world and although I have been talking about it in it’s mineral sense (that can be mined – a type of mineral called an evaporite), let’s not forget that you can also get halite when it is exsolved out of (as opposed to dissolved into) sea water! This can cause Halite to crystallise in sheltered spots around the coast, so keep an eye out for these little white-pink cubes, you may find it more easily than you think!

For more information about Halite please visit the MinDat website.

Galena – Day 22 of the Mineral Advent Calendar

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This holiday season, why not get a mineral every day instead of chocolate? Today’s mineral is Galena find out more about it below..

We are getting towards the end of the Mineral Advent Calendar now so your final preparations for a couple of days filled with family, friends and celebrating must be nearly done. Today is the Winter Solstice, so if you have been celebrating already then Happy Midwinter!! There are many things that you can use to celebrate the time of year, but one of my favourites is crackers, and crackers depend on one thing to make them go bang!

Do you have your crackers yet?

Do you have your crackers yet?

And that one thing is silver fulminate. It’s the chemical used on the strips of crackers that makes them pop as you pull them apart, a delightful mini-firework for your kitchen table! In order to get silver you mine it directly (as in Day 11) or you can mine something with a lot of silver in it, and that is our mineral today – Galena!

A lovely big lump of Galena from Dakotamatrix.com. But the best identifying feature of Galena is it's density - it's unusally dense!

A lovely big lump of Galena from Dakotamatrix.com. But the best identifying feature of Galena is it’s density – it’s unusally dense!

Galena:
Chemical formula: PbS
Colour: Lead-grey
System: Isometric
Hardness (Mohs): 2½
Can you find it in the UK? Yes

Ok I’m starting to think this is my computer now, so as soon as I can get a version of the map to work I will upload it, but needless to say you can find Galena in the UK, to find out where check the locations list on the MinDat website.

For more information about Galena please visit the MinDat website.

Graphite – Day 21 of the Mineral Advent Calendar

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This holiday season, why not get a mineral every day instead of chocolate? Today’s mineral is Graphite find out more about it below..

The second of the UK snail-mail deadines fell today and sorry, if you missed the 1st class post today, then your only option you have to get deliveries done by the 25th is Special Delivery. But in relation to Saturday’s post, you need to get your scissors flying to make the mail!!

Sharp scissors are essential for nice wrapping!

Sharp scissors are essential for nice wrapping!

But apart from iron, you need carbon to make the best steel scissors! The easiest place to get carbon, although it is a common element (an ingedient in many minerals) is Graphite. So our second Mailing Mineral is Graphite! Graphite is also helpful if you want to make sure you have sent all the seasonal cards on your list by checking them off with your pencil!

Lovely graphite crystals taken by John Jaszczak.

Lovely graphite crystals taken by John Jaszczak.

Graphite:
Chemical formula: C
Colour: Iron black to steel-grey
System: Hexagonal
Hardness (Mohs): 1 – 2
Can you find it in the UK? Yes

The only graphote location map I could get to work! From the MinDat website.

The only graphote location map I could get to work! From the MinDat website.

Unfortunately the map showing locations you can find Graphite in the UK isn’t really working, but you can find graphite in all the places where you can find metamorphosized rocks that are rich in carbon, so check all the usual mineral rich locations (Cumbria, North Wales, Cornwall, North West Highlands).

For more information about Graphite please visit the MinDat website.