The half smelts are most likely due to the matte layer. This matte layer is caused by not properly fluxing the ore. Iron or steel is added to the melt, drawing the sulphur away from the concentrated ore, removed prior to pouring into conical mold. This step of removing sulphur can also be accomplished with the addition of an oxidizer to flux, or by roasting, prior to smelting/assaying, in the open air at around 800 F (slight cherry red concentrate color). If you ore does contain Arsenopyrite, the fumes will be toxic to deadly while roasting. I do not know how to scrub Arsenic fumes while roasting.
There are quite a few videos on roasting on Youtube. Mount Baker Mining and Metals has some decent videos. He also covers the smelting process.
With respect
the roasting process of Arsenopyrite
is way complicate it.
and Very very dangerous.
Arsenic is poison,and very deadly.
Please don’t roasting Arsenopyrite is deadly and will kill You.
in low concentration will destroy Your body from inside out .
with respect roasting Arsenopyrite is a deadly idea.
big company avoiding dealing with Arsenopyrite
to work with Arsenopyrite ore
they have to spend lot of money in equipments,PPE,training their employee
because any little mistake can be Your last.
Here in Arizona there is plenty of abandoned mine with huge minerals very rich in gold and silver ,but contains lot of arsenic in it ore.
and No one want to touched.
a big company grab one of those mines.
they constructed a huge building and other thing
and in just 2 years abandoned
because no one want to work for them.
Arsenic is too dangerous,is not worthy to risk your life for any amount of gold or money.
is like the oil rig,drilling in the oilfield is dangerous
the H2S gas is dangerous and in high concentration can explode.
please don’t do that huge mistake of roasting Arsenic rich ore
no matters how rich it is.