Flint-on-Flint Firestarting

For practitioners of primitive arts, flint-and-steel has long been a mainstay of fire-starting.
Better yet, is if we can hit two rocks together and light our fires.
Flint-and-steel is excellent training to learn the technique of making and catching sparks. But what if we don’t have the steel? Obviously, fire by friction remains, but it is relatively time-consuming.
I’ve been trying to identify rocks that spark when struck against each other. Last night, I made some progress.
One thing that helps, is to work in low-light conditions. That’s how I made my latest discovery.
Last night, we had a pile of rocks that we needed to move. As we were putting them in the ATV trailer, I was pleasantly surprised by an orange spark! Time to stop and identify rocks!
The rocks were both quartz, and the one definitely had a substantial amount of red iron in it.
As we continued working in the dusk, sparks were flying everywhere! As we unloaded the rocks in a muddy stretch of road, there were frequent orange flashes as the rocks clattered into place.
Now, it’s a matter of getting good charred tinder close enough to the spark to catch.