Archive for September, 2012

New Location – Arizona Mushroom Ryolite (At Last!)



I can’t believe I FORGOT to put this one on the website – the most important thunderegg from Arizona!  Gawd I am hopeless!  These have been on my shelf for a long time and I might even have shared one on the blog before – but now I have finally put them where they belong on the gallery!  Sometimes erroneously called ‘Mushroom Jasper’, this is actually a type of thunderegg, and probably Arizona’s most beautiful and famous thunderegg. The cores are usually quartz but it is the amazing matrix, pale and sketched with reds and browns, that makes this so special. Because of their extremely free-form shapes, often just a conglomerate of blobs and pockets of matrix and crystal, this is quite commonly used for carving and cabbing, rather less often seen as whole specimens. Both of these here are quite uncharacteristically intact and structured for this location. 

The Earthquake Stone – Mojave National Preserve

Of course, I cant say for certain that this stone went through an actual earthquake – or rather several earthquakes – but this specimen from the Mojave National Preserve sure went through SOMETHING.  This is a tilt thunderegg, where the horizontal layers indicate that it has moved in the ground.  In fact, this is the most extreme tilt thunderegg I have ever seen by a long way.  Most of the time, tilts are subtle, indicating that the ground has moved a little and that’s it.  The story this one has to tell though is somewhat more dramatic.  Some upheavals have shifted it almost precisely 50 degrees in various stages, pretty much turning it on its side.

Here’s my own speculation about it: close examination reveal that the tilt mostly happened quite gradually, without any massive single changes in angle.  Rather, the stone has ‘crept’ slowly (though sometimes faster than others and with a few jolts and sudden changes), causing the horizontal lines to be laid down in a fan shape, starting with the white opal layer and ending with the main central area of banded agate.  However, some fairly dramatic moments also seem to have occurred.  A certain amount of debris has built up on top of the white opal layer – even clearer in other specimens from this location (which follow more or less the same pattern).  A more dramatic shock occurred later, which actually fractured the old agate, leaving a small shard loose, before the fill continued (after a period of fortification banding).

Beautiful New Specimen from California – “Templeton: Highway 46”

Templeton – Highway 46 Thunderegg

A new location for me and I think a very beautiful one, and also very different to other Californian specimens.  This is a rare and somewhat confusing location though. The Highway 46 bed is located, not surprisingly, on Highway 46 between Templeton and Cambria and is apparently still accessible, though rarely offered for sale. They are characterized by an extremely free-form shape, sometimes very complicated and bearing a certain resemblance to the Arizona Mushroom Ryolite.

However, there is another, rather more infamously rare thunderegg from this area known as the Templeton Biconoids, characterized by much neater structures and a significantly different colour matrix, verging towards salmon pink. The speculation goes that these two locations are one and the same, or at least from the same area, though this in not known for sure – the Biconoids being specimens that have weathered out of the original bed and become scattered. Allowing for a certain amount of variation within the bed and for the influences of the new environment on the Biconoids (including sunlight), this seems plausible. These Biconoids are almost unobtainable now, since much of the surrounding land is inaccessible or built over, which is a shame because they are very interesting stones. I don’t have a known illustration of one that I can publish here.

From the Tiniest to one of the Ugliest Thundereggs – But Another New US State: Texas!

Behold the Chinati Mountain Thunderegg – an ugly duckling of a stone that probably wont grow into a swan no matter how many more millions of years it sits there.  However, this is the first and only stone I have ever seen from Texas and just maybe I am being mean!  The greys and browns of that matrix are really kind of nice and I would definitely be keeping my eye on the location in the unlikely event of ever running across more of them – just to see what it is capable of.  This one has a rather nice skinny biconoid structure with a little agate floater in the centre surrounding a cave.

New Location, New US State – And One of the Tiniest Stones I have Ever Seen

Keweenaw / Lake Superior Thunderegg

This has to be one of the most exciting new additions to the gallery in quite a while.  As well as being a new location and a new US state (Michigan), this is the smallest thunderegg I have ever seen by a long way – just 12 millimetres.  That’s about the size of a pea – or halves of a pea!  Yet in spite of that, it is perfectly formed, showing an almost perfect thunderegg structure with a box core and button and a core divided into two areas with a crystal fill at the top – what looks like smoky quartz.  For something so tiny to have such perfect banding and structure is just amazing. I am told that about 1 in 20-25 specimens has this kind of banding.  These beautiful little crumbs can only be found washed up on a short and very remote stretch of beach on Lake Superior or by diving down to the bed itself somewhere beneath the waters. The beach stones (as this specimen is) thus have a characteristic water-worn exterior with whitish seams of core visible. Very few people know where to find them and that makes these almost microscopic but perfectly formed thundereggs a very precious stone.

I am scared to breathe too heavily around these things and will have to get a proper little case for them!  Polishing it was as experience as well since using my gear for such a minuscule specimen was like handling half a pea on a moving dinner plate!  My heart was pounding, I can tell you – but it actually worked out very easily.