The Iridium assay

1 mL (the equivalent of 1 mg of metal) of Iridium Chloride is being placed upon the fluxes with a graduated polypropylene pipette.
An Ag bead the size of = 0.052” has been inserted into the fluxes to eventually capture the Ir when cupelled.

The still hot Ir melt.

The Ir button is at right bottom of broken crucible and is the weight of = 36.75 grams.
I cannot account for the reason so much extra Lead was reduced when the fluxes and furnace heat is the same. It is possible that a more intimate mix of the fluxes and with the activated charcoal contributes to this anomaly.

The cleaned Lead, Iridium and Silver button ready for cupellation.

10x – The IrAg prill still residing in the cupel.
Size of Bead = 0.055”, which only slightly larger than the original inquart.
Notice the black crystal laying in a circular pattern around the prill.

20x – A magnified view of this prill showing the typical snake-skin crystallization of the Ag that is contaminated with Iridium.

30x – a magnified view of preceding image.

30x—A magnified view of the black crystals laying on bottom of cupel, suggesting that there was not enough silver to collect all the Iridium.
Notice that the bottom of the cupel has a different dark coloration of the bone ash than do the other pgm assays.

20x – The Ag being dissolved with nitric acid mixed with water, leaving blacks clinging to sides of the silver prill and on bottom of glass slide  blacks forming in Ag and on grain boundaries of the snakeskin

40x – The microscope focus is on the dissolving prill surface that shows an odd gray coloration.

40x – This image is focused upon the blacks laying on bottom of glass slide as the remaining silver dissolves.

20x – after about 1 hour all the silver has been dissolved leaving behind these shinny black Iridium crystals.