Etching out sperrylite crystals from the matrix

Hi there,

I have a specimen of Russian sperrylite in the chalcopyrite matrix with several crystal faces peeking out. I want to expose the crystals better. Is there another way to etch the crystals out other than with a pick?

Thanks, Keith

In the west it is commonly done by using an air abrasive tool. The matrix that the sperrylite crystals are usually poking out of is chalcopyrite and it is quite soft and can easily be "eaten away" with glass beads. The same method has commonly been used to remove galena from around garnets, bustamite etc in specimens from Broken Hill, Australia.

Rock Currier
Crystals not pistols.

It's not Chalcopyrite. It's usually Mooihoekite ( a closely related Sulfide mineral). You can tell by the unusually rapid surface oxidation effect that occurs very soon after blasting off the material with glass beads - like in seconds.

Chalcopyrite is attacked by alkaline solutions (visibly at pH >9) , and this might also hold for mooihoekite (I haven't tried this, though) .

The pressure of blasting can cause surface cracks to the minerals that are about to be cleaned,so abrasive should be used with rubbing rather than blasting:

Use a knife to remove the matrix around the Sperrylite but make sure you keep a distance-don't touch the crystals.You can mask the crystal with a large piece of tack.

Clean as much matrix you think will be safe and leave some matrix around the crystal.

Take abrasive powder (make sure the material has a hardness closer to the matrix than the Sperrylite!) and use a drill with a brush head to remove the matrix around the crystal.

Make sure the drill is not twisted too fast,don't let the temperature raise.

A good idea would be to create a paste :mix abrasive with some viscose liquid-like dish wash detergent-inert and easy to clean off.

It's much slower method but safer.

Good luck!
-Kostas.

what types of things is sperrylite used for ?.........im doing a report about it and one of the quetsions ae what is the use for sperrylite and i cantfin anything about its uses

Sperrylite is one of the ores of platinum. And you can sell it to mineralcollectors.

Sperrylite crystals are worth more to collectors than their platinum content. The mineral itself, just the massive stuff, or broken crystals is worth only worth the value of the platinum in the material or what an ore buyer or a refiner would pay you for it.

Rock Currier
Crystals not pistols.