Because I don't have Iridium metal on hand I'm forced to hopefully make an alloy of Lead metal and a 99.9% liquid Iridium Chloride (IrCl) standard.
To accomplish this task I begin by cutting a 1 gram piece of 99.5% Lead from a small bar, which is hammered thin and flat. Then I curl up the outside edges to make what I refer to as a boat, as seen in the below image.

This image is showing the pipett dispensing a total of 2 ml of liquid iridium chloride into the Lead metal boat.
Each milliliter is supposed to equal 1 mg of Ir.
I suspect that some Ir will be volatilized as the propane torch heats the liquid.
No metal odor was detected as I drove off the liquid, but could certainly smell the chlorine.
Some caution is necessary to avoid melting the thin Lead edges and thus losing liquid.
When all the liquid has been dried the thin Lead is folded in half and folded again and again as shown below. Then this metal that now contains the residue from the liquid is hammered to somewhat seal-in this reside, so that when the lead is melted it will alloy with the Ir.

The next 5 images illustrate the melting and alloying (Pb & Ir) of the folded Lead metal boat.
Although these images are taken during the hot stage and will be significantly different when the plaster tablet has cooled they nevertheless provide sublimates of this heat range that when compared to Lead or other alloys will be slightly or vastly different and as a result will provide valuable clues for future reference

Just beginning to melt the Lead alloyed button and colors are present. The yellow is Lead oxide.

Difficult to hold the camera, click the shutter and re-wind for next image, while holding the flaming propane torch. Consequently, the melted button not only solidifies but the photography is awful. I have recently ordered a 35mm film camera with auto focus and winding to make it easier to take better images and hopefully reduce the amount of blurred images. However, the primary purpose of these images is to illustrate colors and application which I am accomplishing. Having said that, a better camera will be a terrific asset, but I am still an old body that does not like to stay stationary too well.

Using a minimum of heat, because I am not trying to create sublimates, but mainly to thoroughly melt the metal so that a good alloy will develop. Nevertheless, lavender, blues, reds, greens and yellow hot sublimates form, but quickly fade once the heat is removed.
I am trying to build this library of hot and cold sublimates to not only help me but to aid the serious prospector who wants to have some control over their sampling of potential ore. This methodology worked for the old-timers and I can no reason to abandon the tried and true.

Notice how quickly sublimate colors change as heat dissipates.

10x

This image shows the resultant cooled PbIr alloyed button on the above plaster tablet(s).
Colors of this cold plaster tablet are very close to accurate, excepting shadows and reflective light.
The reddish feathery glob on top of button is probably Lead oxide (Pb3O4) that forms easily when using a heat source (propane torch) that blows considerable amounts of air allowing oxidation of the molten lead.
Direction of torch flame is from right to left.
This button was removed from tablet, reasonably cleaned of adhering plaster and minor slag then cupelled as shown in following images.

The yellow sublimate color is the formation of Lead oxide. The red is a combination of Lead and other oxides contaminating this button (Ag, Ir and trace metals).
This and the following images attempt to demonstrate a simple cupellation procedure that anyone can do with a little practice. Once this methodology is employed there is no immediate need of having expensive electric/gas furnaces to accomplish the normal laboratory setting and task of obtaining precious metal prills from cupelling lead buttons of any size.
For those who may decide to learn to cupel I found that practice was my teacher. Notice the position of intense heat, which is below the molten lead button. I gradually heat the cupel with the Lead button already in place (within the cavity). so that the lead melts only when the bone ash below the lead button is sufficiently hot enough to begin absorbing the molten Lead. Furthermore, too much heat (flame and force) directed at the bead will vaporize considerable amounts of the precious metals, as well as allow the cupel to cool below the heat range of absorption, causing the button to freeze.
Prior to melting the Lead button I place a piece of silver under the lead so that the lead will absorb the silver and the Ag will usually act as a collector of sought for precious metals.

The cupel has cooled considerably, but not quite enough to show the brown stain of the silver oxide around this resultant silver prill. I placed approximately a 30mg bead of silver to collect as much Ir as possible, because according to what I read Iridium does not ally well with silver.

Although this cupel has not cooled to the touch the sublimate colors are changing and a little more brown around the silver prill is forming.

10x
Color of the prill is being influenced by the surrounding cupel stains.
The image shows the alloyed silver prill resting inside the cavity I previously dug out of the cupel to contain the original Lead button.
Although most of the molten lead is absorbed into the bone ash cupel a small amount is also vaporized and can be seen as wisps of smoke during the entire cupellation emanating from the lead button till near the end of the procedure.
I always save the used cupels if they have not been totally saturated with Lead. Usually, when I begin to re-use previously used cupels I scrape away any obvious contamination from the surfaces and only place the new lead button on/in a clean area to conduct tests like this, thus avoiding using new cupels. As long as there is a sufficient amount of uncontaminated cupel surface and the cupel does not crumble into a mess while scraping a new surface and cavity for the Lead bead to be cupelled within then small tests like this one works quite well.
Conducting cupellations like this will cause an unavoidable loss of some silver and possibly other precious metals. However, this method is a quick and inexpensive way to make reasonably accurate tests without having to resort to relying upon laboratory expertise.
Furthermore, if the prospector does not learn how to do simple tests then the prospector will remain at the mercy of those who capitalize upon ignorance.
Notice the crack below and beside the prill. Cracks can be a source of considerable loss.

40x
The crystalline surface of this prill is definitely not that of a normal reasonably clean silver bead. So, at this point I suspect it is safe to assume that some iridium did indeed alloy with the silver.
When this prill is digested in acids I will be better be able to determine with the aid of the microscope and chemicals if iridium is present.

Size of prill = .07” = approximately 30mg.
When prills, such as this one are digested in acids the contents of the prill can be determined with the aid of the microscope emicals.
Normally, based upon what I have read, not only are all the PGMs rare, but seldom does nature accumulate Iridium in rich ores more than a few parts per million. So, this is an exceedingly rich alloy. To discover the various effects Ir or any pgm alone or in combination may make the silver prill appear like several tests similar to this would be appropriate.
Because this prill has such a clean and unmistakable cystalline surface I did not subject it to further melting to drive off possible trace amounts of potential lead. Instead, proceeded by digesting it in 1 drop HNO3 & 4 drops distilled water, all of which resides within a well of glass slide.

40x
Black crystals beginning to show as the silver is ate away and exposing the xtals just beneath the surface.
The chemical activity does not allow me to capture a good quality image without resorting to utilize the streaming video capabilities, which is too time consuming to get set up for.
The microscope images are captured by a stereo zoom Bausch & Lomb #5 coupled to a ccd microscope camera connected to the pc. Although this ccd camera is certainly not the quality of a forensic laboratory, it nonetheless serves me well enough.

40x
Focus is on the black crystals beginning to be cast off and out of the silver prill.

40x
Along perimeter are the gaseous bubbles due to the acid digestion of the silver.
Occasional odor of fresh brewed coffee, but usually there is a sharp, unpleasant astringent smell.
Digestion is slow, further indicating that the prill is not simply silver with mechanically held particles of Iridium. Plus, when super saturation nitrate crystals form their shape indicates a nitrate alloy, further indicating that some iridium has actually alloyed.

40x
The Ag appears to act as a collector.

50x
The iridium metal crystals surrounding the prill as it continues to digest.

70x
Magnificent steel-white Ir crystals.

70x
Same scene as above image except the light source is repositioned to allow a slightly different perspective without all the reflected light.
The dark base color is due to the microscope copper stage surface without the white paper the glass slide usually rests upon to enhance colors and subvert shadows.

70x
This image is focused along a rounded edge of what remains of the prill as it continues being attacked by the acidic water.
These shiny crystalline surfaces resemble what I have seen with what was supposed to be Rh and Ag.
This image clearly illustrates that some alloying has occurred.
Color of the focused area is accurate.

40x
Focused area is almost correct. The prill is actually white, but the reflection of my hand has changed image color.
Notice the rounded and somewhat mammary crystal structure, further suggesting that Ir has alloyed with the silver.