Shiny pebbles

There's a corner of the shop that's set aside for little trays of tumblestones. Lots of places sell them - shops in museums and visitor attractions often have some. Mostly they are fairly common stones that are colourful or nicely patterned - they are very appealing, tactile things.

While their not exactly the backbone of my business, they are a steady seller and occasionally people will buy in bigger numbers. I once had a guy who bought a bunch of quartz and hematite for use as backgammon pieces. People have used them as wedding favours, party handouts, etc. Quite a few buy a selection of colours to put in a dish and look pretty.

I still like finding new ones to put out on the shelves. At some point, I should get an industrial tumbler and start doing my own.

Eye of the beholder

The post the other day about the Gem of Tanzania brought up a topic worthy of a bit more attention. How is a fossil or mineral valued? There's not really an obvious answer. No handy flowchart to follow, no book to look up. There are gemological societies and institutions that will provide assessment and authentification services. For big ticket items, you might approach an auction house. You could look online and try to get an idea of market worth. Even take it in to a fossil shop. All possibilities, but none will give you a cast-iron figure because ultimately it's highly subjective.

Obviously, with some things it'll be a bit easier. Were someone to bring me a Green River fish, for example, I could give them a pretty good idea of retail value. A jeweller presented with a diamond cut in a standard fashion would be able to provide a solid assessment based on weight and clarity, etc. Bring in something slightly more unusual and things get a lot more tricky.

At the show in Tucson, I have bought stuff by the box in a marketplace on one side of the road, then crossed to a hotel where I've found one piece of exactly the same mineral, from the same locality, on sale for more than the entire box I've just bought. Clearly some people are simply more expensive than others, but there is a market for collector pieces - examples of exceptionally high standard - where prices can get scarily high. If there are enough people around that might want a piece then the potential value is raised. Supply and demand. That market isn't always accessible, but it's a factor that should influence any judgement. One man's rock is another man's gem.

Hard labour

I've just bought a big load of stones from a dealer I see two or three times a year. He carries a lot of stock, but I usually buy only a few things in bulk from him - drums of fool's gold, large quantities of rose quartz and so on. It means the price is good, but there's a bit of work involved in sorting it all out.

I also buy large lumps of rough rock which I need to break up into pieces suitable to sell. Again, it's a cheaper way to buy, and you get a nice fresh surface on the individual specimens. It can be a bit messy, though.

Firstly, it all goes down into the basement until I find a suitable time. Then I clear a bit of room and start smashing it all up with a hammer. Usually. The picture is of snowflake obsidian, a volcanic glass with cristobalite inclusions. Obsidian will shatter into very sharp fragments so I put it into a couple of plastic bags when breaking it up. Otherwise I would shred my face and arms into mince. The difficult part is trying to get some sort of consistency of size. Not very easy. This afternoon, when it's quiet, I might have a go at some bacon opal.

eBeards

The Palaeontological Association now has a Facebook group. It's in its early days, but there will be fossil-related discussions and so on. Just so you know.

Rocks fizz

Everyone knows what happens if you leave a dirty 2p coin in a glass of cola overnight. In the morning there is a clean and shiny 1p piece in the glass and a mouse has drunk the juice with a straw. Or might have. I've never stayed up to watch.

I often leave rough rocks in cola overnight to clean them up. Yesterday there wasn't any cheap cola, so I got some Irn-Bru instead and dumped a load of rubies in a bowl of it. I don't know if it worked as well. It's hard to tell. I can't remember if it's the sugar or the acid or a combination. Does anyone know?

Wreked

Administrators of Wrekin Construction, a Shropshire building firm that went bust in March, are trying to sell a stone that had been listed as the company's most valuable asset - a 2 kilo ruby known as the 'Gem of Tanzania'.

This stone was previously sold for £130,000, then valued at £300,000, but had then been re-assessed and traded for £11m worth of shares. It was this dubious valuation that had at times allowed Wrekin to keep afloat. The most a ruby has ever sold for at auction is £2.6 millon - something of a steal compared to the Gem of Tanzania. Prior to sale by the administrators, however, a closer look has been taken at the ruby and it was discovered that its valuation documents, from an Italian gemological institute, had been forged. The full story behind the stone is a long and interesting one involving goat's serum AIDS remedies, Rolls Royces, and Richard E. Grant. Albeit loosely.

Anyway - the ruby has been shown to be a low grade of ruby, in zoisite. I've sold this stuff, known as anyolite or ruby zoisite, for a long time and it's a good seller. Nice contrasting colours - the deep red of the ruby and vivid green of the zoisite streaked through with black tschermakite. I think the most expensive piece I've sold was £50. The Gem of Tanzania's revised value is now £100 and has been refused by the larger auction houses approached. It's now going to be advertised for sale in a couple of mineral and gem magazines. Quite a come-down, but definitely a rock with a good tale to tell.

Addition to the family

An old monkeywoman, Ardi, has been given a bit of a write-up in today's issue of Science. She is about 4.4 million years old, which makes her a good bit older than a later neighbour, Lucy, who's thought to be 3.2 million - still of bus-pass age but relatively spritely. Both fossils were found in the Afar Rift valley in Ethiopia; Lucy in 1974 and Ardi in 1992, along with remains of a few dozen other individuals.

Lucy was an Australopithicus afarensis, while Ardi has the name Ardipithecus ramidus and shows more primitive characteristics. Flatter feet suggest Ardi and her species spent less time walking upright than Lucy's bunch. Her opposable toes and great, flapping hands suggest she was still more of a tree climber than her cousin, too.

It'll need a lot more work to be more certain of where Ardipithecus fits on the hominid tree, but it seems unlikely that they are directly in line with Australopithecus as the earliest of the latter found so far is dated to around 4 million years ago. Seems quite possible that the two had a period of overlapping existence. Maybe Ardi's descendants knew Lucy's ancestors. It'd be nice to think they all played in an inter-genus East African football league together. Probably didn't happen. Remember - this was even before buses and half-time pies.

Probe

Just had another visit from a born-again Christian who has been coming in for early morning discussions of late. He was, at first, a little cagey about revealing his motivation. His opening questions were about the ages shown on the labels in front of the fossils. To begin with, he just said he doubted that the earth was millions of years old but give his reason as being that it felt wrong.

Over subsequent visits, he has talked more about his religion, though, and shown that his scepticism of science is really based on countering anything that may undermine his interpretation of the bible. This involves, it transpires, an estimation of the age of the earth at somewhere between 6-10 thousand years. Back to that again. I know - it's just something of a sticking point with me. It seems to me, admittedly a firm atheist, there can be ways of incorporating new information into a faith and that people should not shoot themselves in the foot by flatly denying the obvious. By 'obvious' I'm not saying the earth is definitely 4.55-4.6 billion years old - science works by constantly revising current thinking - but that an age measured in only thousands of years is easily dismissed as nonsense. There are living trees almost 10,000 years old, and so far at least one example much older.

Anyway - he is a very nice guy and clearly very driven. He is, to his great credit, able to at least listen to my responses to his questions and give them some thought. I suspect I will be seeing more of him.

Treasure

Some guy found a huge pile of gold stuff while metal detecting in Staffordshire. I would like to find something like that.

Quite often customers confuse archaeology with palaeontology and make Indiana Jones jokes. I'm not like Indiana Jones, really. I realise that's hard to believe. Archaeology is concerned with the study of past human activity, culture and society through found artifacts and buildings etc. There is an element of overlap when it comes to the fossil record of human ancestry, but not much. Given humans have only been around for the blink of an eye in geological timescales, it's a small (but very interesting) area of the subject. A good example of palaeontology and archaelogy working together is studying the spread of tools across the continents. It's a useful addition to the hominid fossil record, and within more restricted ranges even the use of specific materials and designs can be tracked. Shows how people were moving from place to place, and perhaps early signs of trading and so on.

Denver

There's a big fossil and mineral show on in Denver at the moment. It's one I've never been to, though is a good size and is a regular for many of my friends. It's tough seeing all the pictures - feel like I'm missing out.

It would be difficult to justify going. I see most, if not all, of the dealers I'd want to at the Tucson show, and I'd have to buy a considerable amount to off-set the travel costs and so on. Same 'problem' with the Munich show and St Marie... One day I'll probably go, just to experience the show.

Mini rex

Quite a few articles around today about a description of a very small tyrannosaurid from around 35 million years before the larger-sized tyrannosaurid body shape started to appear.

Raptorex kriegsteini has lots of the characteristics of its famous relative, T. rex, and importantly shows that the distinctive features such as the skull shape and small forelimbs were in place well before they got all super-sized. These dinos were only 8 feet long, and weighed about the same as my friend Keith. Less than me.

The surprising thing about the discovery is just how little the body plan changed as it was scaled up. There were a few tyrannosaurs around North America and Asia throughout the later Cretaceous, and they weren't all as enormous as T.rex - a good example being Nanotyrannus lancensis, which deserves a post of its own - but the typical features are present in all.

Collecting glasses

Tektites are lumps of natural glass formed from terrestrial rock on the impact of a meteorite. The instantly molten rock is thrown high into the air, cooling and solidifying on the way down, so is often distributed some distance away from the impact crater. Not all meteorites have created tektites -in fact so far there are only a handful of tektite sources.

The first tektites were found in 1787 in the Vltava or Moldau River, in what's now the Czech Republic. These are now called Moldavite, and are perhaps most appealing example. They vary slightly in colour, but are generally a deep bottle green. They're prized for jewellery now and are often cut and faceted for setting. Moldavite is linked to a huge meteorite impact in Germany, the Nordlinger Ries crater, which occurred around 14 million years ago.

Elsewhere, the Chesapeake Bay impact in the US has produced tektites found in some Southern states, a grouping of sites around Western Africa are thought to link to an impact in Ghana and tektites found in Australia, China and South East Asia may come from one huge impact. In this case, though, the crater has yet to be identified and there is a good chance they may be from more than one event.

While the impact theory is almost universally accepted, there are a few other suggestions for tektite formation. The most interesting is that they are little lumps of lava from volcanoes on the moon. As wild as this sounds, there is at least some evidence to lend it some weight. Tektites are very dry. Drier than bone. Drier than a towel in a tumble drier in the desert. Moon lava is also very dry. And so... Well - there's more to it than that. I'm being glib.

Another stone I should bring up here is the controversial Libyan desert glass. Although it was first found a long time ago - tools were made with it in the Pleistocene - it still isn't entirely clear exactly what it is. Prevailing opinion now puts it as a tektite, though the shapes it takes are not the usual tektite forms, it is far lighter in colour and it has a far higher silica content than normal. I can't see how this cannot at least be partly attributed to the terrestrial rock in the area of impact, though. If the meteorite hit a sandstone, might the resulting tektites not be silica-rich? Still lots of research being done on this interesting rock, though.

Out of Georgia

There was an interesting talk at the British Science Festival in Guildford yesterday about hominid finds in Dmanisi, Georgia. The story itself is not new, with the first discoveries being made back in early 1990s, but the talk discussed the current thinking on the finds. You can read a little about it here, but the article is more than a little hyperbolic in its claims that the finds demolish the Out of Africa theory.

The skeletons and skulls date to around 1.8 million years old and are a more primitive species than Homo erectus, the folks responsible for what had previously been considered the first road trip out of Africa, around 1 million years ago. H. sapiens, us lot, didn't get round to heading North until relatively recently, maybe 100,000 years ago. Imagine the packing that went on. 'Look, I'm sure you're not going to need all those loin cloths. Just bring the extra hairy ones; it's probably going to be freezing.'

While still not certain, the Dmanisi finds resemble a more developed H. habilis or possibly closer to H. ergaster. It had been thought that erectus had been the most primitive hominid to make the trip into Eurasia. While the Out of Africa theory had regarded two major excursions from the continent as being the most significant, it had never ruled out any number of others at different times. It seems that these early Georgians had made the journey some considerable time before the more evolved erectus left for pastures new, but that does nothing to undermine the theory's main points, as the species was clearly a bit of an evolutionary dead end.

The article linked to above suggests that at some point the Georgian hominids may have made the return journey to Africa and continued to feed into the evolutionary melting pot. I see no need for this to have happened at all. Seems much more likely that not everyone went North in the first place and that probably the majority of the species stayed at home, where it was warm and they knew they could get tasty antelope.

Anyway - it's a topic I find fascinating. One thing is certain - as more finds are made, more evidence is revealed and we will be able to add to the story of human evolution and expansion from Africa.

Reality bites

Wow - dinosaur teeth!

Awww. They're blunt.

Home alone

Riley, the Mr Wood's Fossils auxiliary, has told me of his plans for the Christmas break. Like last year, the American Idle will be lounging around in his homeland for nearly a month. Such a slacker. This leaves me facing a month manning the shop on my own.

If you come in on a Saturday in the near future, please feel free to berate him for his lack of dedication. And if you come in during late December, please bring me a strong coffee.

None more black

Jet is very black. So much so that they call things that are really black jet-black. (Let's forget for a second that jet can also be dark brown). It has a long history of use in jewellery, despite it being more of a fossil than a mineral. It has - slightly condescendingly -been called a mineraloid. I'm always a little disappointed to be described as a humanoid. It's like I didn't quite make the grade.

Jet is actually a dense form of lignite - a coal. It's thought the best jet is fossilised Araucaria wood, better known as the monkey puzzle tree. Given how it can be found in the stratigraphy, most jet seems to have been initially deposited as driftwood. A softer form was originally laid down in freshwater. Another form of coal, anthracite, is often mistaken for jet, but true jet takes a far better polish than the pretenders.

Whitby, in Yorkshire, has long been a centre for jet jewellery, as some seams around that area provide very high grade material. A lot of material is also washed up on the beaches around that part of the coast, though it tends to be of lesser quality than the material directly mined. It's harder to find now, but there is still enough to keep a few jewellery makers going. Vikings used to come to Yorkshire to get jet, taking a break from their raping and pillaging to pick out a pretty brooch. The oldest jet jewellery, though, is thought to be between 16 and 17,000 years old, and plenty of 10,000 year old stuff has been found in Germany.

Queen Victoria was a big fan of jet. Because it's black and it went with her dresses. Her endorsement saw a bit of a boom in the trade. It's not quite as popular now as it was back then, or in the twenties, but it's still a nice stone. And I like nice stones.

Look!

Advertising is a tricky thing to get right. Because the shop is a little different, I get approached a lot. Newspapers, magazines, travel guides, web promoters, etc. I'm lucky in that I get a little more editorial than I might as, say, a card shop, but it can be very difficult to weigh up the pros and cons of each 'exciting opportunity'.

There are a couple of ways to gauge the effectiveness of advertising, but they can be clumsy and offputting at times. I take out a small and incredibly expensive advert in a tourist brochure that goes out in vast numbers all over the country. I have recently downsized the ad, as it had reached the point where I felt it may have become impossible to justify the expense. At least, with that one, people regularly come in waving the brochure. There are a couple of other Edinburgh tourist guides I go in most years, though I tend to vary it a little.

I also take out the occasional ad in the Scotsman and Evening News. With a newspaper ad, many people may see it, but it's a one day thing, quickly binned. Or recycled, of course. Web promotion seems even more nebulous, but at least some form of site traffic monitoring can be put in place in many cases.

I've recently had a spate of calls from website promoters suggesting I paid for their services last year and that it was time for me to renew. Or even, that i had agreed to split payment over two years and it was time for the next installment. This one was the fourth, and by this point I actually told the guy not that I didn't remember but that I didn't believe him. The first one was a little suspicious, but by the fourth over two months or so, I was certain it was a scam. A hard one to spot, though, as often money paid to push your website can seem like cash thrown into the wind.

However - I've had a few calls recently that I have listened to. I'm sponsoring a rubber chicken in a play in this year's Fringe. Gets my name in the program. I got to name the chicken, too. Woody. I'm going to have a 20 second ad running in the Ocean Terminal shopping centre for the next two years. It was a good deal, though it still added up to a hefty sum. I get to keep the rights to the ad, though, so maybe I'll be able to find something else to do with it. There will be some Mr Wood's Fossils 'advertorial' in Vogue this autumn, too. That was a call out of the blue. Apparently, someone had heard we sell meteorite pendants. Sadly, I won't be making the cover.

Bitten

There's a film out at the moment called Mega Shark vs Giant Octopus. Now, while I'm sure that almost everyone has a soft spot for giant-sized sea beasties - and especially sharks and octopuses - this film will probably not be an oscar winner. Harsh to judge a film on its title alone, but... You know.

I don't know too much about fossil octopuses, but the Giant Octopus that's currently kicking about is the Enteroctopus. A good name, worthy of a film itself. They only get up to about 20-23 feeet long, though. Not really that giant.

Mega sharks, however, are another matter. The undisputed mega shark was the Carcharocles megalodon. It was a relative of the great white - Carcharodon carcharias - and in fact was until quite recently assigned to the same genus. Megalodon, as it's usually called, means big tooth. Do I need to tell you why? Okay. It had very big teeth. No - bigger than you're thinking. No - hold on - not that big. Be realistic. The biggest complete tooth ever found was a little over 7" long.

The estimated maximum length of megs has been the subject of some debate. The best approach is the use the closest living relative, the great white, as a comparative measure. The technique is to scale up from tooth size and although different figures have been bandied about over the years, current thinking puts the approximate maximum length at around 60'. That's similar to a good-sized sperm whale. There have been bigger sharks, but not carnivorous ones.

Great whites attack a potential meal by ripping out a big fleshy lump - ideally the stomach area - and then coming back in for the kill once the thrashing around has abated a little. Megs would consider seals a bit of a light snack and there's evidence they used to attack whales - vertebrae with tooth scars etc.

Like many sharks, megs would have grown teeth constantly, shedding as they became worn, broken or loose during lunch. It's thought they would have had around 250 teeth in their mouth, too, so for every one shark there would have been a great many teeth throughout its life.

Megs died out only about 1.5 million years ago, and while many people would like to think there are a few still about, lurking in the depths, many others are very glad they are gone. Snorkelers and surfers especially.

Lost In Transition

Where are my paper bags?

Twisted metal

One of the things I get asked about a lot in the shop is bismuth. Bismuth is an elemental metal that's grouped with arsenic and antimony. Unlike those, however, it's not (very) poisonous. In fact, one of it's main uses until relatively recently has been in stomach medicines for various reasons. Pepto-bismol, for example.

It forms naturally in a couple of ores and sometimes as nuggets. What draws the comments and questions, though, are the artificially grown hopper crystals. These are made using almost completely pure bismuth with trace additions of other elements to add varied colour to the oxidised layer that quickly forms over the silvery-grey surface.

Only a few people in the world make it, and the process to make decent crystals is a closely guarded secret. A friend of mine bought the business and know-how from a retiring Belgian and is now making his own in his garage in England. A few experiments has led him to the biggest crystals ever made. It's pretty brittle stuff, so once the crystals get over a certain size they can be quite fragile. He buys the raw material in ingots from a company that refines metals. The price has risen a fair bit in recent years as bismuth has gone from being a moderately useful by-product to an increasingly important product in its own right.

It's now being used as a substitute for lead in fishing weights, as an alloy for shot, pellets and plumbing uses. There are plenty of other new uses, but an important discovery made recently will lead to it being used in electrical circuit boards and in solar power cells. Bismuth diodes allow

two-way current flow, which will create far more efficiency in electrical equipment.

Great for global technology, not so great for the price of bismuth crystals.