Is it Basalt?

Well maybe not… after my adventures in Radstock I thought I had 60kg of basalt dust that would provide adequate material to make many a sculpture. But after the first pour (see post ‘experiment #1 – pour’) there seemed to be a significant difference between my hypothesis and reality.  Unfortunately the Radstock basalt was incredibly viscous and we really struggled to get anything out of the crucible.  I had another sample from Iceland which flowed well but I only have a limited amount and sourcing more of this basalt isn’t the easiest solution!  Bristol University’s Earth Science department offered to analyse the two samples so we could work out what I have.  To my artistic eyes there is an obvious slight colour difference, but apart from that I feel only microscopes have the answer.
One way of solving the problem of viscosity is to add a flux.  This is a common practice in metal casting as it helps the impurities rise to the surface and allows the metal to run freely.  The question is: what flux would work for molten basalt?

Rocks are made from a multitude of minerals.  These minerals in turn are made up of elements from the periodic table.  Basalt is commonly made from calcium-rich plagioclase feldspars, pyroxenes and olivine and sometimes also has ilmenite, magnetite, biotite, phlogopite and feldspathoids.

I think this is one reason why my Radstock basalt and my Icelandic basalt are so different – there are so many possibilities for their chemical composition.  After  speaking to Prof Kathy Cashman she suggested using lithium tetraborate as a flux.   I have ordered said chemicals online and will bring them with me to the next pour.