Mineralogy

Geology Photo of the Week #29

Matt Herod April 8, 2013

The photo this week is of another self collected beauty. I collected this piece below at the Marmoraton Iron Mine in Marmora, Ontario a few years ago. When I found it none of the garnet crystals you see were visible. They were all covered by a thick layer of calcite. I could just make out the edge of a broken crystal at the side. However, I have been collecting at Marmora a lot and I knew that this had the possibility to turn out beautifully since at this quarry calcite often hides terrific and undamaged crystals below. You can still make out a little bit of it here and there (it is yellowish white). The key is to just get rid of it. Luckily, for me and many other collectors of Marmora minerals calcite dissolves easily in hydrochloric acid. So cleaning a find like this becomes a simple matter of placing it in a basin of HCl and waiting for the magic (chemistry) to happen. After a few days, and a few changes of the acid the result is what you see pictured below: a beautiful cluster of 1-1.5cm grossular garnet crystals, with some magnetite veins, minor epidote and left over calcite.

(Photo: Matt Herod)

Unfortunately, the garnet crystals of Marmora are not gem quality or anywhere near it, but they do form very attractive crystals of which I have a large, large number after years of collecting there. Marmora is also a great place to collect epidote, pyrite, calcite, pyrolusite, magentite, ilmenite, marcasite and actinolite. All of which are common and relatively easy to find with a bit of work. e.g. sledgehammering.

The quarry is larger than the town of Marmora!

Cheers,

Matt

p.s. Watch this space for EGU2013 updates starting tomorrow!! I’m really looking forward to the Fukushima press conference.

The 46th Ottawa Gem and Mineral Show

Matt Herod November 22, 2012

A few weeks ago I went to the 46th annual Ottawa Gem and Mineral show. I have always been a dedicated mineral and fossil collector and shows like this allow me to indulge my inner collector and drool over all the fantastic specimens. I have been to a lot of shows, all local such as Kingston, Peterborough and now the Ottawa show, but there are tons all over the world. In fact, I would speculate that most large communities have a mineral show. Indeed, some like Tuscon or Munich are renowned among the mineral collecting community. The Ottawa show was far more modest than those other “supershows”, however, it is still a great show with lots of vendors selling and displaying all sorts of great samples.

A view of the show. (Photo: Matt Herod)

Therefore, I thought it would be fun to share the show and post some pictures of the best specimens that I saw/could not afford. In fact, I think the only part of me that had a bad day was my wallet as it was significantly emptier for my having been. I guess poverty is just one of the sacrifices I’ll have to make for this blog.

I hope that you enjoy gratuitous photos of minerals.

I’ll lead off with this show-stopper below. A superb piece of Stibnite showing two episodes of growth from Wuling, Jiangxi Province, China. It was selling for $250.

Next up is this great specimen of Magnetite. It hails from Mina Huaquio, Potosi, Bolivia and I am not sure what the price was, but I would estimate over $50 for sure, if not close to $100.

Boom! Next: $$$$$$$$$$$$$$$$$$$$$$$

The following piece may be the most spectacularly piece of oxidized Bornite that I have ever seen. It hails from Mexico.

For our next show-stopper we have this beautiful, light pink, Halite from Searles Lake, California. It is going for about $50.

A terrific piece of Scolecite from Neral, Maharashatra, India. There is also some Stilbite in there and maybe some Apophyllite. This piece is massive. I couldn’t get a scale because it was behind glass, but it is about 40cm wide and 20 high and was selling for about 6 months salary for me, a grad student, and a month’s for a geologist with a real job. This the the last drooling photo of a mineral before I show some other stuff from the show. It is a tray of pyrite crystals from Navajun, La Ruja, Spain. Great, sharp crystals, and going for affordable prices. Not everything at these shows is super expensive.

Next, we change gears a little. I am now going to stop with the gratuitous mineral pics and show some pics of the fossils on sale and some of the other knick knacks that were available.

First up is a plate of fossil fish, Diplomystus, Knightia and Priscara from Kemmerer, Wisconsin. They are around 55 million years old and are selling for $1700.

Next is a complete mold of a Pseudogygites latimarginus from the Blue Star Quarry, Bowmanville, Ontario selling for 45$. This is actually a decent price for this fossil. I know that it is only a mold, but finding a complete specimen of this species is rare in Ontario. I have done a lot of collecting in the Bowmanville area in the same rocks that hold this fossil and only every found tails and heads.

There was also lots of jewelry at the show and cut gems. I am not usually interested in this sort of stuff, but I happened to be there with a jeweler. So he was pointing out some of the interesting cut gems available. He bought a few and I am looking forward to seeing what he makes with them.

I have been going to rock and mineral shows since I was a kid and have always enjoyed them. They are mostly attended by the general public and hobbyists. Not very many geologists make it out to them. I know that very few of my colleagues managed to attend despite good intentions. I have to lament this as a lost opportunity for public engagement. As geo-bloggers we continually wail about how best to reach out to the public and the lack of geoscience reaching people in their day-to-day lives. Honestly, I can’t think of a better opportunity to reach people of all ages and backgrounds better than at a rock and mineral show. Attendance normally numbers in the thousands at these events and people unanimously love them and leave feeling interested about minerals and fossils. Shows like these are the perfect opportunity for geology departments to reach out to the public and make them aware of other aspects of the science beside consumer driven ones. I encourage anyone who reads this to consider attending a show near them. For any academics that read this I encourage you to set up a booth from your department to raise awareness about geoscience research.

Sorry for ranting at the end. I’d really like to hear about other people’s experiences at mineral shows. Do you think they are a missed opportunity for geology outreach?

Thanks for reading,

Matt

The Wooden Wall

Matt Herod October 5, 2012

It is once again time to write about geology and classics and the incredibly important impact the geosciences had on the ancients and their way of life. My previous post on this topic can be found at my old blog location as the post: The Odyssey and Geology. I’ll begin by relating a story:

Themistocles (Wikimedia Commons)

The two fleets, the Persians the the Greeks, which was composed of the navies of all the city states, but mainly Athens, met in the narrow Strait of Salamis for a final and deciding battle. The Persian king, Xerxes, was so certain of victory that he set up a throne in nearby Athens to watch the battle. The true architect of the battle though was not Xerxes, but the Athenian Themistocles, a politician and general. Indeed, it had been Themistocles who had convinced the Athenians to build a navy of over 200 additional ships in the years prior to the war and it was he who stationed the Greek navy in the Strait of Salamis, which was advantageous for the smaller Greek navy. The battle proceeded according to Themistocles’ plan and the Greeks were able to out-maneuver the Persians in the narrow strait and succeeded in decimating the Persian navy. This was a great blow to Xerxes who fled back to Persia with much of his army. The next year the Greeks were able to defeat the remainder of the Persian army driving them out of Greece and winning the war. Salamis was the turning point of the war and saved Greece from certain doom.In 480 BC the ancient Greeks were faced with their biggest threat in history: the invasion of the Persian king, Xerxes and his armies. The Greeks, despite being horribly outnumbered had fought bravely but been defeated in the Battle of Thermopylae. The Persians then advanced through Greece nearly unchecked and conquered Athens. However, the Persians knew that to fully conquer Greece they would have to do so at sea as well as on land. Things were looking pretty grim for the future of ancient Greece at this point.

Source: Wikimedia Commons

The hero of Salamis, Themistocles was a very persuasive politician as well as tactician. In fact, it was he who convinced the Athenians to build the 200 triremes (ships) that made of up the bulk of the Greek navy and can be credited with saving Greece. The credit cannot be only given to Themistocles though. In fact, the idea came from the Oracle of Delphi. The Greeks were very worried about the impending Persian invasion and decided to consult the oracle for advice on how to win the war. The oracle cryptically answered along the lines of the “wooden wall will save you”. Clearly, this answer could not refer to the building of an actual wooden wall since that would be stupid and obviously could burn down. Themistocles interpreted the oracles advice to mean build a navy. Unfortunately, the ancient Greeks had the same problem with national defence requisitions as governments do today and money for such a venture was not easily at hand. However, geology was going to come to the Greeks rescue in the form of a major silver discovery at Laurium, a small mining community just south of Athens, providing the Athenians with enough money to afford a new navy. Without the discovery at Laurium it is possible the navy would never have been built and ancient Greece would have fallen into Xerxes hands. Ergo, geology saved ancient Greece from total domination by the Persian empire.

So now what about Laurium?

Miners in Laurium. They were all slaves. (Source: Wikimedia Commons)

Google Maps

The Laurium silver mines are located just south of Athens and are world renowned for the excellent mineral samples the area still produces in addition to its storied past. The mineralization is of lead, zinc and silver and is associated with the emplacement of an igneous body within metamorphosed sediments. The ore occurs mainly within marble especially at the contact with other metamorphic or igneous rocks (www.mindat.org). The list of minerals found in the Laurium mining district is a mile long and it is actually the type locality for about a dozen minerals as well, making it a world class mineralogical site. The mineral Laurionite is named in honour of the location. In addition to the minerals occurring in the mines there are a host of others that occur in the ancient slag piles left by the Greeks. The slag has reacted with the sea water used in processing the ore in ancient times to produce a suite of new and unusual minerals there as well.

Agardite, Laurium, Greece (Source: www.mineral-forum.net – Used with permission)

Diaboleite, Laurium, Greece (Source: www.mineral-forum.net – Used with permission)

Conichalite, Laurium, Greece (Source: www.mineral-forum.net – Used with permission)

Nealite, Laurium, Greece (Source: www.mineral-forum.net – Used with permission)

Annabergite. Larrium, Greece. (Source: www.mineral-forum.net – Used with permission)

The ancient ore processing techniques of the Greeks were obviously primitive relative to today’s, however, they were still able to extract both lead and silver from the ore. The process essentially involved numerous washes with water in a sloped basin. The heaviest material was collected and smelted, and the resulting slag was carted away and dumped. Since then the slag has had a few thousand years to oxidize and this process has resulted in the growth of all sorts of interesting minerals like the ones pictured above. Laurium is still geologically relevant today from the perspective of the mineralogist or mineral collector as the area still produces some world class specimens.

It has always amazed me how deeply geology is integrated with our lives today, what with our dependence on natural resources for nearly everything. However, it would appear that this is not a new phenomenon and that geology always has been and will always be a crucial part of our lives.

Thanks for reading!

Matt