Many thanks to everyone who responded to this, on and off list.
Based on the experience of others, I think these devices might not be
practical in the setting I was proposing, so thanks for the advice.
Geoff: good point about the sampling strategy, which I fully admit I
hadn't thought through properly before I posted. But, unfortunately,
few archaeologists are competent in the use of the vanning shovel,
myself included, so that's not really viable in this case either. A pan
might work, I guess, using the Mk 1 eyeball to spot the Sn..
Cheers
Phil
On 19/08/2017 10:13, Bruce Grant wrote:
> Good morning all.
> Having used one of these (Thermo Niton) extensively in a mining environment I can add a few thoughts to those already made. The point regarding the limited are of examination is most important. In say a hand specimen left behind by the 'old men', it is quite possible to have an indication of both a barren and conversely a rich mineral content particularly when examining for cassiterite. The comment by Geoff regarding the vanning shovel is the significant point.
>
> The reported 'elmental' composition is just that, an indication of the elements present not the presence of an ore mineral i.e. tin will be reported but not whether that tin is present as an oxide, sulphide or silicate even if it is within, for example, a garnet matrix.
>
> All of these things the portable instrument will not tell you. In short, there is no substitute for experience.
>
> Best wishes
>
> Bruce
>
> -----Original Message----- From: Geoff Treseder
> Sent: Saturday, August 19, 2017 7:00 AM
> To: [log in to unmask]
> Subject: Re: XRF and XRD hand held
>
> Hi Phil,
>
> Ian Hodkinson seems to have confirmed what I suspected about these devices.
> What I would say however is that a sample should be a sample, there
> shouldn't be any prior knowledge of its content to say that it is worth
> analysing. The sampling method should be undertaken in a way that gives you
> something representative of the material that you wish to know more about.
> The pan and the vanning shovel are much better tools for for looking at tin,
> they are cheap and give more meaningful results and much more useful
> information.
>
> Regards
>
> Geoff
>
> -----Original Message----- From: Ian Hodkinson
> Sent: Saturday, August 19, 2017 2:28 AM
> To: [log in to unmask]
> Subject: Re: XRF and XRD hand held
>
> I use them regularly at work (mineral exploration). Hand-held XRF
> analysers are great at what they do but the effectiveness is limited by
> a couple of factors. They have a very small field of view, only a few
> square millimetres, which means they work well on a homogenised powdered
> sample but wouldn't be good on something like a grainy alluvial
> material. You can get round that to some degree by pattern testing but
> that increases the time. They are notoriously bad at detecting nuggetty
> material like gold and thus presumably cassiterite grains in a rock or
> alluvium sample. Experience suggests to me that the Olympus ones are
> asomewhat more user friendly than the Thermo Fisher Niton ones.
>
> WIth XRDs I only have experience of using them to identify discrete
> mineral species. Once the sample gets beyond a handful of mineral
> species the identfication of the contained minerals can get very
> complicated although there is software for that these days.
>
> You can certainly rent them in Australia - in the UK though ? Then
> there's all the X-ray user licence/possession licence bureaucracy to
> wade through.
>
> Hope that helps a bit
> Cheers
>
> Ian
>
> On 19/08/2017 1:33 AM, Phil Newman wrote:
>
>> Hi,
>>
>> Does anyone have any practical experience of XRF and XRD hand-held
>> analysers?
>> Can they be used to detect all types of ferrous and NF metals and do
>> they give instant results on site?
>> I'm looking at detecting unprocessed alluvial tin stone and dressing
>> waste in a clay context within an area of post-med tinworks. It would be
>> easier to have some idea of what we put in the sample bags before
>> shipping them off to a lab for full analysis.
>>
>> Also, is it possible to hire this kit?
>>
>> Thanks for any help.
>>
>> Phil
>
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