The last Wednesday of the month can only mean one thing (apart from in December, where it was New Year’s Eve) SciBar at The VAT & Fiddle.
This month’s talk was by rock stroker Clive from the British Geological Survey and he was talking about sand. Not just any sand but only the tip-top best of the best sand.
However, the evening got off to an inauspicious start. If the speaker needs a laptop for their presentation then they usually bring one. However, Clive thought that one was provided which led to a bit of panic. Fortunately, the pub had one so we had some PowerPoint slides to look at during the talk rather than just a small pot of sand.
As a layman whose only experiences of sand have been a beach, a long jump pit and a gold bunker, I was happy that the presentation began with the basics – what is sand? I didn’t realise that technically sand can be made of anything; it’s actually all about size. To be sand, the grains have to be between 0.063 and 2 millimetres. Any smaller and you’ve got silt. Bigger and it’s gravel that you’re looking at.
Silica sand, also known as industrial sand, consists of quartz and is differentiated from building sand by being purer. Also, you can’t make glass with anything else.
There are a number of things that you need to check in order to see if your sand is suitable to make glass with. Are the grains clear? The composition, shape, size, refractory minerals and contaminants all have an impact on the characteristics and hence the usage. It’s also worth noting that ideally you’d like a slightly angular shape to the grains as this melts faster making it better for glass production.
Ideally, you’re looking for a silica content of 98.5-99%. However, deposits are usually only around 80-85% quartz. Hence the sand needs to be processed. For example an acid bath with remove any traces of iron.
This processing makes a big difference to the value of the sand. Initially you might get between £70 and £80 for a tonne. However, after it has been processed you can get up to £280 per tonne.
Clearly, there can be big money in sand, which is why the British Geological Survey have been out mapping the UAE. At the moment they import their sand for glass manufacture from Saudi Arabia.
So, Clive and crew have been out in the desert sampling sandstone, gravel plains and even sand dunes (even though the sand in a dune isn’t suitable for glass) They think that they might have found just what they were looking for but it’s all a bit hush-hush, top secret and so that was where the presentation ended.
During the break between the talk and the Q and A session, Clive passed round some premium Saudi Arabian sand and his hand lens so that everyone could have a really close look at it. At the start of the evening, I’d not really been sure what his hand lens was as it looked like a whistle hanging around his neck. Although I have no idea why a geologist would bring a whistle to the pub (sounds like a Lewis Carroll riddle – Why did the geologist take a whistle to the pub?)
Anyway, it was amazing how clearly you could see the individual grains through the lens. Some were perfectly clear while some were frosty. The majority were pretty round but there was the occasional pointy grain as well.
Clive handled the Q and A really well – here’s a guy who really knows a lot about sand. Fortunately, he also managed to reassure us that we are unlikely to run out of sand in this country anytime soon even though we dig up nearly four million tonnes of it every year.
If I have one small nit to pick, it’s that the presentation could have used a bit of editing. It went on for over 30 minutes and probably didn’t need quite so many pictures of quarries in it – reminded me a little of someone’s holiday slideshow and if you’re going to show quarries, I feel that you should definitely show some that have been used for Doctor Who.
Still, it was another fascinating talk on what could have been a very dry subject. Sand? Deserts? Dry? Sorry.
February’s SciBar is on TUESDAY the 24th and the title of the talk is “Black Holes and Extra Dimensions”