I am pleased my letter on the Dryhead Agate has been published. This makes it clear that ordinary banded agates are colloidal in origin and not formed from solution as suggested
previously, before a low temperature was established by the isotope results. These indicate agate formation took place at 50°C.
Mexican Coconuts are the agates for which most data exist being the subject of a thesis. A recent study of rocks in Skye provides information on the bentonite, the mineralogy of which is relevant.
The bentonite includes colloidal silica as well as montmorillonite, a clay mineral. It will be present in Mexico as well as at the base of the Skye lava field and is the obvious source of any agates present.
For some time I have been considering the idea of gold digging in the UK, the recent US documentaries I have to admit are fuelling my ambition. I came across a gold prospecting map from a website and thought it may be worth a try. As I live in Scotland I tried there first not having to travel far. I went with the correct tools and enthusiasm to find that actually it is a long drawn out process and not very profitable (if I were in for a living). It did make me realise that all those years ago when our ancestors traipsed off abroad to make their fortunes, how hard it must have been, and in my case for what. I wanted to write to you not just to tell you my story but to highlight to any hopeful gold diggers out there that actually it is a good day out but don’t expect gold at the end of it, and whatever you do don’t spend a fortune on tools (I have learnt my lesson).
Thanks, Rock n Gem
Tom. A (recreational) Gold Digger
(Ed. Shhh..we’re also fans of a little gold, gem & fossil prospecting, but please make sure you adhere to rules and regulations when it comes to ‘collecting, perhaps some of the readily publicised locations are where gold used to be!)
I've recently purchased some of your magazines and noticed that there are occasional articles
related to the collecting of minerals and fossils, my children seemed to have developed a passion
for stones and taking then to the local beach doesn't seem to be 'enough' for anymore do you have
any suggestions for collecting elsewhere because they would really like to explore more?
Dear Rock ‘n’ Gem,
I feel sure that a reader out there who sees the letters pages may be able to offer an insight into unusual Agate forms, having a keen interest in Agates and their formation, I thought your readers may be interested to see my recent purchase. The Agate concerned is a tube agate reportedly from the Woodward Ranch in Texas, USA and it has some interesting details, an Agate is unusually formed where the banded formation is clear, but these are very different. You can see in the photograph the tubes formed within a very clear agate, this is also very 3 dimensional and more akin to the Jaspers that occur in Rhyolites, it may be that the temperature difference in the original Matrix being more silica rich produces these internal shapes.
happy to receive letters, but email is quicker!
Dear Rock n Gem,
Having been an avid show goer for some years I’ve noticed that the number of mineral and fossil
dealers at events seem to have dwindled along with the range of larger ‘display pieces’. Having a
house full of stones I’m now looking at finding new homes for smaller pieces and replacing them with
larger items. Obviously being able to view large items at a show is easier than venturing overseas with
a large suitcase.
(Yes it does appear that you do have to search farther a filed for more unique pieces, perhaps the new
Rock, Gem n Bead and other show organisers might create opportunities for exhibitors to have a ‘large
gallery’ at events - Ed.)
letters issue 64
Dear Rock and Gem, (ref issue 61)
The investigation of temperature formation of agates is largely confined to chalcedony. Quartz crystals are less suitable. A better example than the agates illustrated would be provided by a photo of the outside of an agate. This provides dykes, water may pass in or out as they act as channels.
Dear Rock 'n' Gem,
Issue 61 Autumn 2013 received. Barry Taylor's first letter makes the false claim that temperature differences come into agate formation. This cannot be the case. The second letter repeats the claim.
Our letter writer was asked to draw attention to the colloidal origin of agates. It is inevitable that excess fluid is produced by such an origin. Silica in solution is not involved in agate production. This would involve different temperatures. These do not come into the picture.
Agates are all the same, being formed at 50'C this needs to be understood.
To continue about Mexican Coconuts(Issue 59) these were obtained in large numbers and were marketed as geodes especially if they provided amethyst. The agate fractions were included in the isotope study. The result agreed with the others but were not published...
happy to receive letters, but email is quicker!
Dear Editor, Please forward to Barry Taylor.
Dear Barry Taylor,
Having been made aware of your agate interest by your letter to Ed., may I ask your advice on sourcing rough material
similar in colour to attached image. This is part of a 17thC German sword hilt so no doubt was originally found in Idar,
Any thoughts, please?
Sincerely, L W