Use something, a tin lid or sheet of birchbark, to catch and hold your debris. This photo shows the materials I used. From left to right, they are: pyrite sample from Baffin Island, tinder fungus inonotus obliquus, flint. They are sitting on a tin lid in a mixture of pyrite debris (silverish in photo,) tinder fungus debris (brownish in photo) and flint debris (more grey and chunky.) Did I mention this method is messy?

Begin by taking 2 chunks of tinder fungus and rub them together briskly, letting the dust and debris settle onto your container. Alternately, you could use a piece of tinder fungus and the flint piece.

Once you have debris in an area roughly 2"x2", hold your pyrite and flint a few inches above the tinder and prepare to strike the flint against the pyrite, as shown. Here is the position of the materials prior to striking the pyrite with the flint. I use a flint & steel-like technique, but I let the sparks fall to the debris pile below. Strike to generate sparks and let them fall into the tinder. Pay close attention. The sparks are small.

Any that catch will need to be blown on immediately to let them grow. This photo shows the coals emerging. The first is a tiny reddish blot underneath the flint in the lower left corner and the second coal as a dark brown spot between the flint and pyrite among the brown tinder fungus debris. If you look very closely, you can see a slight wisp of smoke coming from the right side of the second coal.

This photo shows one larger coal after the two have been combined. It has been also been blown on and covered with tinder to make it grow.

Remember that 2 stone firestarting generates a lot of debris and too much pyrite dust is a "spark killer." You may want to occasionally agitate the debris pile, shaking it gently to let the pyrite dust settle. If you wish not to use the debris pile and strike against the tinder fungus directly, you may want to clean it of pyrite dust frequently.