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Agatology 101 – Class 15 “Question Number 1” What, Exactly, is a Lake Superior Agate? Well, if we’re going to define what a Lake Superior Agate is, we should first figure out what a “regular agate” is – you know – the good, ol’ fashioned, generic variety. So, to do so, I go to the holder of all knowledge… The sacred tome of eternal information… The lost texts of geological wisdom. I go to… Google. I type, “What is an Agate” and here’s the response I got: 1. an ornamental stone consisting of a hard variety of chalcedony, typically banded in appearance. Trouble is, that also defines banded chert – which is not an agate. And Jasper, when it’s banded – and also, not an agate. Okay, so, that’s the dictionary’s response inside Google. Maybe that isn’t fair, so we should ask another source. Wikipedia describes it more in detail. Agate /ˈæɡət/ is a rock consisting primarily of cryptocrystalline silica, chiefly chalcedony, alternating with microgranular quartz. It is characterized by its fineness of grain and variety of color. Although agates may be found in various kinds of host rock, they are classically associated with volcanic rocks and can be common in certain metamorphic rocks If you read this definition, there are 3 keys that may not be readily apparent. Key #1: chiefly chalcedony, alternating with microgranular quartz. Key #2: they are classically associated with volcanic rocks. Key #3: It’s what they don’t say that’s the real key. If we break this down, Key #1 clearly indicates that banding is required to be considered an agate of any type. The phrase “alternating with microgranular quartz” clearly indicates “banding”. Next, being associated with volcanic rocks is an interesting key but, to some degree, it doesn’t fit with Lake Superior Agates (I’ll discuss further, deeper down in the lesson). And, last, Key #3 is the biggie. What isn’t said is what’s really said. Let me explain. Defining what an agate *IS* can be dicey. Most definitions you’ll run across use similar words: Alternating, Variegated, Banded, Silica, Cryptocrystalline or Microcrystalline Quartz, Chalcedony (pronounced Cal’-said-own-knee – or as some people who don’t know how it’s correctly pronounced say, Cal-said’-a-knee). This pronunciation is an intentional swipe at my good friend Bob whom has corrected me, time and time again, to his way of saying the word. I’m entirely kidding that “they” are pronouncing it incorrectly. It’s much like Poe-TAY-toe versus Poe-TAH-toe. Just depends on where you learned the word. Anyway… I digress. The problem in defining what an agate *is* - lies primarily with the fact that we don’t yet know exactly how agates form. There are lots and lots of books and websites out there that pretend to know (and explain to you) exactly how they were formed. However, if you read Bob and Dan Lynch’s book (commonly referred to as the Agate Bible), they explain that no one yet knows the exact method in which agates form. Other so-called “experts” assign a single paragraph or two and “explain” how they were formed. The sad thing is, however, that every theory put forth to date (as of the typing of this class in January of 2019), has holes in it. This, by definition, presents problems in attempting to define what an agate *is*. Terms like alternating or variegated assume banding. This is not always the case. This ignores a Plume agate. And what about Eye Agates? Or Tubes? Or Stalactite Agates? Or Moss Agates? Or Sagenitic Agates? Or the ever-enigmatic Skip-an-Atom Agates? These are usually ignored in most theories of formation and on most websites. They are the agates that most educators would prefer to not talk about because they throw the proverbial monkey-wrench into many of the theories of formation and, therefore, the definition of what an agate actually *is*. Terms like microgranular quartz make the assumption that every agate has microgranular (larger crystals that appear different to the observer) quartz mixed with the micro or cryptocrystalline quartz that makes up an agate. Again, not always the case. This ignores a paint agate that is entirely red. Or a phrase like, “a hard variety of chalcedony” is an oxymoron. ALL chalcedony has a hardness of 6.5 to 7 on the Mohs Scale of Hardness. There aren’t hard nor soft varieties of chalcedony. It’s all a 6.5 to 7. (Seems like Google, the sacred tome of eternal information maybe has some learning to do?) ☺ Here’s another sticky wicket. As was mentioned before, agates are classically associated with volcanic rocks. This is absolutely true. They are normally associated with volcanic activity. However… There are Lake Superior agates found in Iowa. And southern Minnesota. And even as far south as Kansas. There were never any volcanos down there. Nor iron deposits to stain the agates the distinctive “red” color that’s usually associated with LSA’s. So, without volcanos, iron deposits, or the basic building blocks of Lake Superior agates, how are they down there? Glaciers. They were pushed down south. So, while agates are classically associated with volcanic activity and rocks, remember – forces happen, naturally, that move things around. Agates CAN be found where there was no volcanic activity. So, now that we don’t know what an agate is, let’s further complicate things with, “What is a Lake Superior Agate, specifically?” That should be easier and more clearly defined because it’s a subset of “agates”… right?? Nope. Lake Superior Agates are typically named as such because of the carnelian (the red colored microcrystalline quartz in an LSA). Iron was introduced into the agate while it was forming and it stained the stone the redish color you see in a classic Lake Superior Agate. But not all LSA’s are red or even contain any carnelian. Defining what an agate *is* becomes something elusive. Extremely elusive. Some agates are translucent. Some are not. Some agates are banded. Some are not. Some LSA’s are red and white. Some are not. Some LSA’s contain microgranular quartz. Some do not. Some agates are variegated. Some are not. Some LSA’s have “teeth” or flakes. Most do not. Some have circles called eyes. Some do not. Some have tubes that hollow. Some aren’t hollow. Some don’t have tubes at all. Some are blue. Some are green. Some have plumes. Some were formed in a seam. Some were formed in a cavity called a vesicle. Some have a hole in the middle (making them a special agate called a geode). Some do not. Some have needle sprays. Some do not. Do you see the difficulties in defining these stones that God has given us to obsess over? Trying to give a simple definition that includes all of these amazing natural gems and includes all their differing properties, is nearly impossible. In fact, it hasn’t been done yet. Anywhere. By anyone. The only way to know if something is an LSA or not is to look at it. It’s experience. It’s learning under someone who knows each variety and is able to assist you in seeing the differences. It’s getting outside and looking at THOUSANDS of stones. It isn’t just a matter reading a book or two. Or even a college course or two (I’m sorry Dr. Ojakangas, I absolutely loved your courses and I learned a TON). But, there’s simply no substitute for first hand, on the ground, experience. So, the next time you’re in the Twin Ports – or in Minneapolis – or anywhere else Lake Superior Agates are found, reach out to someone who has been looking at LSA’s for most all their lives. Talk with them and have them go out picking with you. Most of us would love to take time to help you – and show you real-world examples of the different rocks and minerals here in the Northland. Yes, keep reading the lessons. Yes, keep learning from every source you can (making sure they are truly legitimate and not just parroting what they’d heard once). But always remember this… “It’s not what you don’t know that gets you in trouble. It’s what you KNOW – that just ain’t so. THAT’S what get you into trouble.” Learning from people who’ve loved geology their entire lives and have the experience to back up their explanations. That’s who you want to help you learn the answer to “Question 1”: What is A Lake Superior Agate? Copyright © 2019 – Agatology, LLC and Glen Bayless. All Rights Reserved. .

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