|Monthly Tech-Tip |
Alternate Names: 3B, PR#3 B
High temperature clean buff firing stoneware clay mined at Ravenscrag, Sask.
Analysis updated July 97.
There is some argument whether the mineralogy should be muscovite or illite. Here is the comment of one technician: "With regards to illite or muscovite, the only way to categorically
differentiate between the two is to determine the layer charge (most easily by electron microscopy) which I didn't do. In this sample, the mica component has no detectable expandability which suggests a high charge mica with very little depotassification typical of muscovites. Also, the x-ray scattering domain size is quite large with minimal disorder which you seldom find in illite but expected for muscovite. However, the kaolinite in the sample is extremely fine as one would see in fireclays. 41% quartz in the sample is accurate. You can easily verify this from your chemistry by checking the contributions of muscovite, kaolinite, smectite and K-spar to the total SiO2, and constraining potassium to
muscovite and K-spar, and Mg to smectite. From my experience, a high plasticity and the apparent illitic properties that you see in the clay is most likely due to the discrete smectite content (8%). Note that the activity of smectite is several orders of magnitude (up to 10 times) greater than the finest kaolinite or illite."
424 Ba ppm
34 Sr pmm
24 Y ppm
10 Sc ppm
249 Zr ppm
1 Be ppm
65 V ppm
Pre 2006 Analysis:
Plainsman extracts 6 different sedimentary clays from this quarry (Mel knows where the layers separate). The dried test bars on the right show them (top to bottom). The range of properties exhibited is astounding. The top-most layer is the most plastic and has the most iron concretion particles (used in our most speckled reduction bodies). The bottom one is the least plastic and most silty (the base for Ravenscrag Slip). The middle two are complete buff stonewares made by mother nature (e.g. M340 and H550). A2, the second one down, is a ball clay (similar to commercial products like OM#4, Bell). A2 is refractory and the base for Plainsman Fireclay. The second from the bottom fires the whitest and is the most refractory (it is the base for H441G).
Plainsman Clays did 6 weeks of mining in June-July 2018 in Ravenscrag, Saskatchewan. We extracted marine sediment layers of the late Cretaceous period. The center portion of the B layer is so fine that it must have wind-transported (impossibly smooth, like a body that is pure terra sigillata)! The feldspar and silica are built-in, producing the glassiest surface I have ever seen at cone 6 (2200F). Despite this, pieces are not warping in the firings! I have not glazed the outside of this mug for demo purposes. I got away with it this time because the Ravenscrag clear glaze is very compatible (similar thermal expansion). But with other less compatible glazes they cracked when I poured in hot coffee. This mug was the beginning of an exciting project the sieve out +325 mesh particles any make many more pieces.
Clays that are not kaolins, ball clays or bentonites. For example, stoneware clays are mixtures of all of the above plus quartz, feldspar, mica and other minerals. There are also many clays that have high plasticity like bentonite but are much different mineralogically.
|Materials||A3 Stoneware Clay|
B Clay Data Sheet