OK, so having spent several sessions looking at the way in which we can use energy to excite.

Electrons?

Around our atoms and how those electrons will.

D exciting various ways in.

Or move between shelves to stabilize.

The Atom.

With the consequent release of energy which is characteristic and can be measured.

It's now time to sort of throw another idea into the mix and to think about how.

How or other mechanisms we can use to actually study the composition of our materials?

And the first of these is neutron activation analysis.

And.

Newton activation analysis is pretty heavy duty.

Physics.

And we don't need to worry about that too much.

It helps to understand roughly what's going on.

But the intricacies of the process are so great.

That we're certainly not going to cover them in an hour or even less if we can push through this to understand the applications of this which are really give us an opportunity to start to build on our understanding of applications a bit more in terms of are the possibilities of analysis.

But it is important to understand the basic principles and.

Like other forms of analysists that we've looked at so far.

We are looking at putting energy into a system.

And we're going to measure the energy that comes out.

In this case, the energy that we're going to put in comes in the form of high energy neutrons.

And we're going to bombard our sample with them.

The energy that is going to come out is in the form of high energy gamma Rays.

And these will be released in a variety of stages, which we'll talk about.

The important thing to realize the principles of benefits of neutron activation over most other techniques, and it has many drawbacks, but its principle benefit is that.

We're putting an enormous amount of energy into it into this sample, and so a pretty enormous amount of energy comes out again.

And as a result we can measure.

Very precisely.

That energy

and because we're dealing with characters, we're going to be dealing with characteristic energies. Just as we were with when we're looking at.

Analytical tools which are based on the use of visible light on X Rays. We are able to. We're able to distinguish.

Using by looking at the different energies of radiation that are being emitted, what kind of samples are in are what kind of elements are in our sample.

And because we can measure very precisely individual emissions.

Because of that high energy, we can very precisely characterize the composition even of very.

Small components.

Of our sample matrix.

So that means we're into trace an microtrace elements suddenly.

No.

Really, really, there is very very few techniques which even come close to neutral activation in terms of its precision.

And limits of detection for minor trace elements.

So what does the process look like?

So we have an instant neutron which is going to hit our target nucleus. That's the sample.

And the instant neutron is going to come from some sort of neutron source, and in most cases that source means a nuclear reactor.

Which immediately raises one of the big problems with this technique.

If you need a nuclear reactor to do your analysis.

You are significantly limiting the amount of the sort of the number of places in which you can do that.

You're also evidently going to be raising the cost of the analysis quite significantly.

Nuclear nuclear reactors for very obvious reasons are quite heavily controlled.

It also to some extent limits the kinds of the kinds of the measurements that we can make on this, because if you see here what's happening is our target nucleus is being struck by an instant Neutron.

And that neutron is binding.

Through a process of inelastic collision, it's actually ends up bound into.

The compound nucleus.

With a resultant.

Increase an enormous increase in the energy within that nucleus. It's suddenly unstable, you've broken apart its normal structure and.

It's not very happy about that, and so it will immediately reconfigure itself or almost immediately reconfigure itself.

And release energy as soon as it can.

And that emission, usually in the form of a Gamma Ray, a high energy gamma Ray is called a prompt Gamma Ray. Now we can measure those theoretically if we can get our instrument measuring instruments to the nuclear reactor, but that is relatively rare.

Possible and certainly applied to archaeological material occasionally, but relatively rare.

What we usually do is rely on a second stage. Now up to this point, we've got energy going in. We've got energy coming out. We've got excitation of sort, and we've got the excitation and release of energy.

So that's fairly familiar. The next stage is where the process neutral activation, sort of.

Diverges from the standard and hopefully relatively comprehensible by now. Principles that we've been dealing with.

Apart from the fact that it's already not dealing with Electrons, but it doing this new clearly.

And that's 'cause the second stage in the process is. Results from that country configuration of the Atom.

And often ends up have in the production of a radioactive nucleus.

A nucleus which has an extra neutron. It suddenly or a number of extra neutrons Maps.

And has.

As a result.

Is going to decay overtime and the concept of half-life the time it takes for half of the number of a particular Atom, particular radioactive isotope.

To decay.

Half of that often, but you know sample that is, is the way in which we record the sort of decay rate of.

Of our elements of our radioactive elements.

And you should be familiar to this from the radiocarbon dating principles there of.

Anne.

And these have life Scarff lives can be in the order of a few seconds or many thousands of years and so.

The depending on the isotopes that are produced during this process.

Will depend on what which of those we are able to measure.

And we are able to measure them because what happens when they put the these isotopes will decay.

Is that they will go undergo a series of emissions. Perhaps they often, probably most commonly beta emission.

Where you're emitting an electron and leaving behind an extra proton in the nucleus.

Often with a good deal of extra energy, and so the resultant emission of Gamma Ray, which is sort of delayed gamma Rays, we call them in this case.

Which is what we would measure.

But the kinds of there are various other forms of radioactive decay as well, which we won't go into. We don't worry about it. What you can you can assume is that the the the.

The things we're going to measure are the delayed gamma Rays that are emitted by this process.

The result is a product nucleus which is actually not the same as the original nucleus because it has an extra proton and therefore is another element. It's one element further up in the periodic table if you like.

So in the case of carbon, what you end up with is nitrogen. After this process finishes.

And you could look up other examples that's less important.

What's important is that there are a number of phases. Let's go through it again. We have instant neutron.

So using a.

We can measure about.

70% of the elements in the periodic table.

But

no technique is perfect, and like all techniques na has major pluses. An major minus is perhaps the greatest of it's sort of limitations.

Is the requirement to.

Access to a nuclear reactor.

Or at least a as substantial neutron source.

The numbers of neutral nuclear reactors around.

Pretty low.

And falling at the moment.

These are extremely costly inst installations to maintain and.

And they need to be decommissioned after a certain amount of time.

That is also an extremely costly actor enterprise, and so access to nuclear reactors is in high demand.

And consequently very expensive.

Another significant costs in terms of time is the reading.

This is a long process. Now you're looking at count times of several hours.

Looking, you're looking at readings taken several days apart because you're trying to capture different suites of elements.

Which have different.

Ranges of Halflives.

You also have to store this material after you finished under this, this the material doesn't stop being radioactive, just 'cause you stop measured it measuring it. Some of these elements that have been re radiated these secondary sort of products, these activation products.

Are radioactive for hundreds or thousands of years.

And so you need to store this material safely and securely or.

Will be able to dispose of it safely and securely, and these have significant implications for your laboratory and really serious implications of legal implications in terms of your.

The requirements the statutory requirements for dealing with this sort of material, so that's something to be considered.

On the plus side.

You get a simultaneous spectrum, which is great, so you don't have to sequentially count. You can. You're counting relatively no relatively low numbers of emissions.

So you can count them sequential sets simultaneously.

You can also theoretically, as long as you don't mind it being radioactive afterwards. You can theoretically do this non destructively. I mean it's not common because you end up with a radioactive object, but you could stick an entire pot in your radioactive reactor and measure emissions from that pot.

It's your gamma. Rays will be emitted.

From throughout your object.

And.

They are so high energy that they're not going to be absorbed by it again, so you're going to be measuring.

Across that whole spectrum of the whole sort of the whole thickness of your vessel, the whole thickness of your metal object could theoretically theoretically be analyzed in that way.

So you know it could be a very good way of doing bulk chemistry, you think, but of course you're looking at something which takes a long time, and in fact both chemic bulk elements are almost never measured within a.

With the emphasis put firmly on the.

Trace and minor trace elements.

Of course you get extremely good sensitivity for many elements and very good precision and accuracy as well, which we of course need to monitor using calibration and sort of standards and standard reference materials to compare with to ensure and allow us to report the accuracy and limits of detection that we are achieving.

There are some interferences, but they are by no means as significant as the ones we discussed for some of the other techniques.

However, some elements are really difficult to measure and extremely difficult to measure precisely.

Some don't form radioactive isotopes.

And some are just just of just a challenge.

And unfortunately for na, some of those challenging elements are.

Elements that, as archaeologists were often quite interested in.

Lead.

Bismuth magnesium calcium

Silicon.

Zinc as well.

These are some useful elements in many cases.

But if we look at the range of the detection limits in our, you know across that the periodic table there are listed below here in parts per million.

You can see why it's particularly powerful technique for some of these elements, like Iridium.

You know you're looking at tiny amounts that you'd be able to detect.

For others, not so much calcium, Silicon phosphorus. You're really looking at elements which would be probably better off analyzing even with eds.

So ultimately

we are.

In order to get a fully rounded analysis, it's likely we have to apply more than one technique because no single technique is really ever going to be suitable for everything. There's always pros and cons. There's always issues with particular elements.

Or overlappings in the Spectra or whatever the issues. Maybe they are going to affect.

Our.

The choices that we make.

As we go, we choose the different one, little techniques that we're going to use in our analysis.

Now, in terms of things which affects neutrality, racing one of the key things is of course half life. So it's the sensitivity of our equipment is our is going to be is of our readings is going to be determined by our ability to actually measure within a reasonable time.

The half life of date. Sort of the emissions as a result of the decay from our various elements.

And so just to give you an example of how this works or doesn't work in some cases if you're looking at copper, you're looking at radioactive isotopes, which will decay with a half life of 3 1/2 hours in the case of copper 61 or twelve 1212.7 I think hours in the case of 64 copper 64.

Nickel 63 has a half-life of 96 years.

So that's not really going to be one we can measure.

Nickel 65, however, we can measure.

Because that has a half-life of just 2 1/2 hours. So depending on which.

You know where what we're dealing with. We can plan our analytical protocol accordingly.

But inevitably, choices have to be made, and that means tradeoffs between sensitivity and time.

In terms of the actual setup for measuring, we don't actually have a very complicated setup for an A. We don't require one. We require a setup which actually looks pretty similar to.

The one you'll be familiar with by now from Xref from energy dispersive analysis in.

And an SCM eds system.

And that's because we're measuring a continuous spectrum of energies which are striking our detector.

Detectors here it's cooled by.

Laser pointer and we're not it's our detectors here cooled by this Christ at this big load of liquidation.

It's feeding out information to preempt fire, which is going through the various sets of processing electronics to a multi channel analyzer which is giving us our output. Just giving us our spectrum.

The main difference is the detector itself, which is not a Silicon lithium, so the control lithium detector, but a germanium detector.

And the reason why germanium detector is necessary is because of the energies of the radiation that we're measuring. The energy of the radiation is such so high we're dealing with remember gamma Rays which are right at the top end of the electromagnetic spectrum in terms of energy. Very, very short wavelengths.

We are dealing with material which would immediately overload.

A Silicon lithium system.

Now we need something which is more suited to this type of energy and so we use a germanium detector, but they're relatively widely available and the whole setup is something which museums have in the past and still some museums do have their own system set setups for dealing with their own sort of measurement systems.

Now, in terms of the applications of this, this technique in archaeology.

Some of the main ways in one of one of the major ways in which this is used is the analysis of pottery.

And specifically, the analysis of pottery provenance.

And there have been some big centers who have been very active in this work.

And because we're dealing with the need to access a nuclear reactor, whereas these other techniques are pretty much available, as long as you have the wherewithal to acquire an instrument or get access to one so they can be done almost anywhere.

It the required for.

Do active means that we have a bit more limited in the sort of options?

But the big centers that were doing it in terms of universities and museums.

For archaeology were the British Museum until about 96 Hebrew University until the late 90s.

Berkeley, you missed you. Mr Manchester had did a large amount of analysis.

Missouri.

In particular, bond had a reactor, and and Democritus in Athens as well. One of the major Centers for the study of archaeological ceramics in the Mediterranean.

Another really important.

Sir, analytical use is in the study of stone, particularly sidian.

And Obsidian analysis and na have had a very.

Productive relationship over the years.

One which has allowed. Actually it's actually allowed the recognition.

Of the viability of using other techniques to explore stone provenance.

It's allowed a really robust test testing.

Of the application of, for example, portable xref to the study of Obsidian, which has been a great one of the great success stories of that.

That technique, but based really based on solid background work in On A.

To characterize sources and to understand the significance of variation between them.

There's actually some.

Entire issues of Archaeometry devoted to both stone and.

And to Obsidian analysis well.

Stone and Obsidian. Sorry stone. Obsidian and ceramic analysis as well, so that's worth worth checking out if you're interested to follow those up a bit more and more detail.

Useful resource for the future.

Terms of meta analysis. It's not hugely widely used.

Then the research reactor at outside Warrington, which was operational for a time, did some very sort of some work on metals of various kinds.

And there's been and Missouri 2 have done some.

Slowpoke in Canada.

And the teams working there did quite a lot of work looking at relationships between.

First Nations communities and incoming settlers looking at hat demonstrating sort of distinction between a compositional distinctions between metal that was obtained pre and post Contacts, and so forth.

But it's not quite so common.

In general.

The University of Missouri. It's worth mentioning actually has a really excellent website.

And they give some really nice sort of simplified, simplified discussions of the technique and some of its pros and cons. There's also some more advanced kind of discussions of how this process is. Is is measured, and that can give you sort of somewhere to follow up on from this lecture.

There's also.

There's also a very good database of material Missouri House, the old used you missed.

Database as well as other databases which allows access to the mid to actual data as well to work with it can be really, really useful if you're looking in the future.

So what does a setup like this actually look like? Well, we've got our reactor here. The reactor outside Warrington, Oregon, as was.

And you've got billot.

You scientists here, he is at his fabulous computer and.

You looking at your analyst setup here.

And.

Between and little setup and scientists is a big old LED wall.

Because remember, we're dealing with really high energy radiation here. It's not good for you.

Andso

protection is required.

However, as long as you're monitoring staff at carefully so you're making sure that there is that they're not being exposed to too much radiation, then you know it's it's a manageable setup, which as we said can be can be achieved even within sort of the museum environment.

And.

So this the system for actually measuring different.

Sort of measurement process is worth just going through a little bit more detail, so you have a better sense of how this works and the first stages we say is take your sample. You put it into a policy in vial, or perhaps an aluminium capsule.

And then you irradiate it in your reactor. And that takes quite awhile, so you are radiating it for two or three 8 hour days.

After a couple of days when the sample is really very radioactive indeed and considered too hot to handle, as it were too hot to transport, it is sent to the museum. This is the British Museum system for dealing with, so this is this is a radiation happening at the reactor Ascot in the early 90s.

On arrival, the first count is made of short lived isotopes such as sodium, potassium, calcium, arsenic.

Timity

lanthanum.

Samarium pink ytterbium



Lou Tanium value I think, and NP neptunium.

So you're looking at separate. They're rare earth elements. I mean, you know it's a struggle to remember what they are to be honest.

But there's the kind of issue really commonly used to explore things like pottery provenance. These are your called your rare earth elements.

So 18 days later.

A second count is done for longer lived I soap, so I stopped with longer half lives which consequently need to be counted for a longer time.

So doubling our counting time at this stage.

And here we did. Measuring elements like scandium.

Chromium iron cobalt rubidium cesium.

Barium cerium.

Europium

TB terbium maybe hafnium tantalum?

And PA.

Possibly protactinium, but don't hold me to it.

They are counted, and again, we're dealing again with with some of the more common elements, but some of the rare earth honest and in fact you know we have to remember that most of the time.

Analysts are focused only.

On trace elements.

So majors, minors even aren't really being measured there, focusing all of their sort of analytical interest in developing a protocol for the measurement of those trace elements.

So once we've done those, those counting the ones with accounting, then the spectrum processing in the computer. Well, it used to take for four hours for 65 samples.

I'll hazard a guess that that time has significantly decreased since 1996.

If the difference in my computer between now and then has anything to go by.

But

the result will be the same and we can't really cut down the counting time. So even though processing time is dramatically reduced, our counting time is still a major major factor to consider.

Yeah, this is a. It's a significant amount of of analysts time.

So it's expensive.

So what are we looking at? Well, we're looking at a spectrum.

Related to a sample of pottery.

And you can see.

That you've got on the left, you've got your accounts here on a log scale now.

And you can see your energy on the X axis.

And if you think about back to xref when you're looking at similar kind of graph.

Can just counter Spectra.

You're looking at the upper limit of xref being somewhere here.

So really quite significant energy differences.

Really quite major differences really.

Is it really quite lovely?

OK, so.

We have

individual peaks you can see identified here, and I hope you can recognize that what you're seeing are some incredibly sharp peaks reflecting really why this technique is so successful.

In its ability to work with sort of mine elements really distinct, well resolved peaks.

So let's think about the difference. Some of the differences between we talked about sensitivity. We talk about some of the issues with overlaps, and so for the lack of issues, overlaps or limited issues overlaps, I should say perhaps with na in comparison with some of the other techniques we looked at. But if we directly compare AA and one of the techniques which quite widely came to replace, replace it in analytical sort of protocols within museums and.

And universities.

Then we compare the best thing to compare with this, probably AES.

And comparing with I, CPA S or as in the case here at Liverpool MPs.

We have similar.

Sorts of sort of issues are involved, so.

Sensitivity, well sensitivity for AES is.

Not as good as na for a number of reasons.

But it is improving.

These days, sensitivity. If you were dealing with solid samples, would probably be more or less equivalent.

But of course.

With.

I, CPA, S and MPA, yes, we're dealing with dissolution methods, so you know that we are introducing.

With diluting our sample in.

So a factor of 1000 times dilution, we're dramatically reducing the the realities of water detection limits will be.

For our material.

Complex dissolution also is a complex process. It requires us to think about concentrations, weights.

It tries us to be relatively skilled.

Analytical chemists.

In the laboratories of relatively high levels of lab skills required.

Na, he doesn't require any dissolution at all. We can just stick our samples in. We can even take our whole.

Patar hole.

Bronze axe along. As long as we don't mind never seeing it again.

If we think about.

I CP, however, we can do something which is really never.

Realistically, never done with na, which is to look at.

Major minor elements as well.

And relatively quickly.

Ice PS is also relatively cheap and MPs as we saw as if you watch the video again, which remember it's the process of.

Extracting nitrogen for our plasma from the air really makes it a lot cheaper.

At a is really not very cheap. It's really very expensive. It's very expensive not only in terms of access to the nuclear reactors, but also in terms of analysts time, transport costs, and storage. Afterwards all require all our costs should be factored in.

And make it really one of the most expensive techniques. Subst out there.

It's also very. It also takes locked. It's also very time consuming as a process, so you know it's it's tradeoffs. As always between these techniques.

A few years ago, there's direct comparison was made between these two techniques, so here looking at a comparison of calcium as analyzed by I CPA S on the left on the on the Y axis and na results for the same samples.

On the X and you can see that for calcium.

Although na isn't particularly good at measuring calcium, it's not a very efficient use of analytical time.

When is measured?

It corresponds very well with CPS results.

He got an R-squared linear relationship of.

.9 ish, which is really pretty good.

Titanium, on the other hand, not so hot. You can see their point 2.3, really.

Really kind of rubbish, and that's largely cause of the.

Relatively poor sensitivity and precision obtained on the AICPA, yes, for titanium.

So.

In terms of direct comparison, yet there it says again, it's all about tradeoffs and making decisions based on what your analytical now.

It's.

In I'll send a link to a video for looking of setup.

For the analysis of Medieval Statuary.

But I just wanted to talk through a couple of examples which show up some of the.

Sort of strengths and challenges in.

NA

analysis

and also some good research practice as well.

The first of these is a study of a geological material, limestone.

From a number of medieval quarries.

And.

It began with the aim of trying to explore the trade in Limestone.

Across France and elsewhere, and.

An interest in the ability to perhaps.

Identify material which had been exchanged more widely.

Pops across the channel.

Or

and also to help with the reattribution.

Of provenance to architectural pieces, sculpture, and so forth.

Which had which was known in museums in various countries.

But which for which the provenance had been lost, or was rather vague?

And as you can see, the analysis of this material here using you can see this plotted against two Canonical Canonical discriminant functions, which are effectively compressing data of multiple variate variables in multiple different elements into two day 2 two dimensions. So we can plot and consider it, and you can see that these are showing us some really very good groupings.

Yeah.

The ellipses here covering sort of 98% of the data.

Showing complete separation between the groups with the exception, I think one point from sang DM.

Adele the desert in here.

But I'm sure the authors have an explanation for that. Come Rd is off hand anyway.

But at this scale, you know you'd expect to be able to identify variety at this scale, even with well with the variety of different techniques.

The.

The authors then went on to actually sort of push the limits of the ability to distinguish material to look at coal.

And a series of sites around it.

So here you have.

A series of sites series of queries.

Her reveal, Montville Fleuris, her own Lamela Dairy Queen, French pronunciation perfect there. My father would be so proud.

But you can see that.

At this level.

It runs into some challenges, but Even so.

The ability to distinguish.

Groups like Keliki, Henryville, perhaps broadly and Lamela, Dearie. You know, it is a pretty impressive.

Sort of pretty powerful tool at dealing with this kind of geological material.

You know, we can really begin to pull things apart, and if we look at some applications that in terms of the identification, the Attribution of Reattribution.

Of.

Origin to material which is now found in Saint Louis Saint Louis Art Museum in America. This architectural boss, just labeled France can be very confidently attributed.

To the quarry harrisville.

Helping to re establish its connection with its origins.

And the same applies to some stature. Here an example from the Metropolitan Museum we saw more of that in the video. You will if you if you look into it.

Now for geological material, it works really well.

Because not very much has really happened to that material since it was extracted from its quarry.

And.

But that means that we can still directly link them together.

With pottery for which na has, of course been extremely widely used.

That is not always.

Necessarily possible.

People do things to pottery. They add stuff to it. They change.

The relationship with.

Between geological source.

And ceramic fired ceramics.

However.

I just want to show you one example.

Seems quite a good one. It's also very accessible. You can access this freely online.

It's a paper by.

Carrigeen Osborne

which is looking at.

Ways away to explore possible relationships between different interregional relationships in the first Millennium BC. Looking at a particular class of pottery, a particular type of pottery to paint, white painted, and by Chrome pottery, which is typical of Greek geometric and sorry, Greek Geometric, Cypriot geometric and superior cake periods. Looking at 8:50 ish to 600 BC.

And it's a type projects find very, very widely across Cyprus and across the.

Northern southern part of Anatolia.

And it studies, in particular a group of this pottery in the Amuq Valley.

An attempts to explore the possibility of.

Of.

Both tracing connections between different areas of Cyprus and the possibility of local production.

Of this material in somewhere in southern Anatolia.

And it compares analytical data from the ceramics.

From three excavations in.

The Hammock Valley and from a wider data set.

From both legacy data.

And analysis undertaken on.

Well provenance material from the Oriental Institute in Chicago.

And compares that with geological samples from.

So Alicia, this North and the plane to the North here.

Some Antonia, the Hammock Valley and Cypress.

And.

The analytical approach is very interesting 'cause it shows good practice.

First was undertaken and nondestructive.

Program using.

Broken fragments of vessels well provenance vessels, and analyzing the brake to ensure that the slip and paint material tests.

We're not affecting the composition.

It.

Then select from.

Major groupings within that.

A number of samples for na to help to confirm those analysis and also.

Uses those to compare with na results on geological material.

And the results from the xref survey with the identification of this Alpha and Beta Group. Here you can see.

And to show that the correlation between this Alpha and Beta Group as identified by X or F and as shown by the smaller range of.

And a samples.

Corresponded very closely in the case of the beetle group with.

Play some Hammock Valley.

Now, there was noted that all three regions had Alpha Alpha, sort of.

Style pottery Alpha sort composition poetry, but the beta was only found in the Valley and a couple of sites in northern Cyprus, and so that was allowing them to be able to think about.

The movement in relationships of these places more specifically.

Using these techniques together to try to improve our understanding and using him as a way of linking together materials and sort of ceramic tools and geological ones.

And this is something which people have tried to do for a very long time, and one of the sort of key, sort of.

Challenges here.

Reflected very strongly in the work of Hans Mommsen from the University of Bonn.

Who is very much a physicist.

And so.

Na as a chemical and chemical animal generally is the really the way of dealing with troublesome human error, as in.

Technological choices.

And understood to try to develop a standardized system for dealing with all pottery analysis, and particularly interested in Mycenaean pottery given.

From memory.

But

really, what was lacking from this was an interest only in Geo chemical fingerprinting.

With a sort of overlooking.

A variety of issues to do with not only to do with burial environment change, but also critically to do with human.

Human behavior, human choice.

And there's a number of things to read up following on from this. There's some excellent work on.

South American poetry by Hector Neff and Co. In the reading list.

Which shows why this should be treated with great great skepticism. This view that we can always a true provenance, and that Providence is inherently telling us something geological.

There's a couple things to read up on this which I should recommend. Hans Mommsen's paper on problems in pottery looking at integrated approaches and comments on the analysis of the kill at of material from the current Commerce by books dedicated Coughlan day. Looking at how not only human action, but also subsequent alteration products can be really affect the way in which things chemical group even from a kiln site. 'cause remember if we think about.

What we're trying to achieve when we're doing connection. This classic approach is to find a kiln. Sites characterized that kill on sight and then compare it with material found elsewhere. But if your kiln site itself is suffering from specific local alteration products, alteration of material, then perhaps elsewhere it may not be the best thing to compare it with, or maybe will be the most successful results.

Shane.

And as I said, the other one to look at is Hector Neff looking at Yucatan Port Tree, which is showing effectively showing that you have.

Groupings, even if they're not geologically significant.

Do correspond often with tradition, strong traditions of production, so we can still get somewhere along this line, perhaps in terms of problems, but it may not be as simple as thinking of it in terms of geology.