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Mineral Magic and a Geological Exploration Through Time

“Where is it made?"

I get this question a lot, and for good reason! Everything pottery related at Apricity Ceramics is made by me (Sophia) in my parent’s basement in Atlanta, GA. And that's that, right?

Wrong!

Indulge me while I take the question a little further, because you may be surprised to know just where some of the minerals that make my pottery possible come from. Some were mined pretty close by, some far away. But believe me, they were all made a long time ago.

Before we get into the nitty gritty of my slip combo, some important info is that any clay body is a combination of clays, feldspars, and silica. Each plays an important role.  Since I’m making a porcelain body (although might wont be a crisp white), my slip needs to have around 40% clays, 25% silica and 35% feldspars.

First, a little reminder of our geological time scale

Silica, also called quartz sand or flint depending on where you live (in terms of ceramic supply), supplies silicon dioxide to ceramics. Silicates are the most abundant mineral on earth which is great because we use a lot of it in ceramics!


It’s the major glass former in a glaze and clay body, but its melting point is 3110 degrees Fahrenheit, which is crazy hot. Other chemicals are added to help lower that melting point (and of course do other things but…)  ‘In other words, silica acts like gravel in concrete and provides the structure a glaze or clay body needs.’ 


It's mined by US Silica CO. in the Eastern US from the Old Red Sandstones created about 400 million years ago during the Devonian Period. Isn’t that just wild!

Tennessee #10 is a ball clay and gives the slip plasticity. What’s unique about this ball clay is that it has low impurities, fires super white (because of low iron content) and has a high amount of kaolin. All of which you want  when you’re creating a porcelain clay!

It won’t surprise you to know that Tennessee #10 comes from (that’s right) Tennessee. In fact, it comes from Henry and Weakley County, TN about 2 hours west of Nashville.

Ball clays from this area are from 40 to 45 million years ago during the early to middle Eocene Epoch (the Cenozoic Era). “It is not uncommon to find black carbonized imprints of fossil leaves and other plant debris in the clay." 

  

Tile #6 Kaolin, otherwise known as Georgia Kaolin, is the most plastic kaolin available in North America. It makes a clay relatively strong while in its unfired state (among other things, but this is the rock star quality). It supplies silica, alumina, titanium, and a little iron.

 Tile #6 Kaolin deposits are found on Georgia’s prehistoric shoreline, where the Atlantic Ocean weathered down the crystalline rocks of the Piedmont Plateau. 50 to 100 million years ago, during the Cretaceous and Tertiary periods, a quick drive to Macon would have put you at the beach.

 

Nepheline syenite is a feldspathic, igneous rock that contains soda feldspar, potash feldspar, nepheline and some other good stuff.  In the ceramic world, we all just refer to it as neph sye.

Its acts like a feldspar (flux) for ceramic purposes. It doesn't supply too much silica (remember, silicas melting point is crazy high) so it’s added to bring the vitrification point of both a clay and a glaze down. Our neph sye comes from Canadian Precambrian rocks in the Greenzone belt, at the Blue Mountain in the Kawartha Lakes region of Ontario-- Formed an incredible 1300 Million years ago

 

Back in the day, there was a chemical called G-200 Potash Feldspar and it came from Monticello, Georgia. But in 2013, after 57 years of mining, the area ran out and the ceramics world panicked!

G-200 had a high potassium content and low iron content (which means it fired really white) and everyone was trying to find a chemical substitute, and quick.

That's how Mahavir Potash Feldspar entered the chat. Imported by Laguna Clay Company, it’s mined in Rajasthan, India most likely in the Ajmer district (although there’s not a lot of information about it out there).

I reached out to the company, but getting an email out of the blue asking for their location because I want to know from which era the feldspar was geologically created may have been a bit weird for them 🙅‍♀️.

My best guess is the mine sits somewhere at the top of the Aravalli Range, which has its origins in the protozoic era, and is one of the oldest geological features on earth.