stairs made from dirt and linseed oil

I came upon this image in another thread ... this is glenn kangiser's house in california. I remember these steps - he told me it was just dirt and linseed oil:

"Dirt" is a pretty mild term for it... it looks like seriously dense hardpan next to the stairs, or in arid California maybe caliche (I don't have direct experience with that). I suspect more clay than anything else. Gorgeous work, anyway!

Yes, several years ago, maybe ten, my partner painted linseed oil on the hard earthen threshold of our external door. I've gone through two carpets just inside the door, but that linseed-threshold has stayed pretty solid throughout, and is only maybe now starting to show some wear. I don't know further details of what was in it, sorry.

Yes. A lot of clay in that soil. I am impressed though. good idea for someone with high clay soils.