When grinding with a glass muller, one can’t help but notice that some rocks grind up with ease, but others require a bit of work. A particular purple found in Londonderry was very difficult to reduce (and the noise in doing so was horrific!).
Once the grinding was finished strips of paper were coated with the pigment mixed in egg tempera binder. These strips will be kept for future record and also compared against the results from the light-fastness test.
Not knowing their permanency yet, I am still very excited about the colours that have appeared. There is a range of yellow ochres and brown/red ochres, but even some pinks, greens and purples. All are wonderful to see and I look forward to the possibility of making use of them in upcoming works.
Special thanks to Fred Walsh, Department of Earth Sciences, Dalhousie University, who was kind enough to send a sample from Copper Lake for consideration.