TerraSkin is paper made of stone! It's actually mineral powder + resins formed into sheets of varying thicknesses indicated in points: 10 pt and 12 pt are the thicknesses I favor. It is translucent like Mylar but a creamy color.
I use it for silverpoint drawing primarily because it is beautiful to work on but also it requires no surface preparation. The sheets can have some flaws: linear scratches across the surface likely due to the method of manufacture (?) Once I know where they are, I adjust my silverpoint application accordingly by working around any lines I may find. Shallow flaws are quite easy to disguise in the finished piece.
Though it is "stone", the surface is delicate: easily damaged and unforgiving if erasing is necessary. The dark joke is we botanical silverpoint artists never erase: we just turn our stray marks into another element like a flower bud or berry!
TerraSkin also accepts pastel dust - my favorite technique for applying a touch of color to my silverpoint work. The artwork in my Blog header, "Horrida" (Agave horrida), is a larger silverpoint on TerraSkin (11" x 14") The one shown here is a smaller work (8" x 6.5"), "Sun-catcher" (Agave attenuate)
I use a light box to transfer my original line drawing to the surface. I then began the piece by applying light layers of silverpoint using a shallow elliptical application rather than the more traditional cross-hatch approach. I shape the silverpoint tool into a rounded tip for this; and sometimes to cover larger areas, I use a blunt-angled tip. My way gives me a smooth, even tonal coverage. TerraSkin accepts many layers, so I achieve a fairly broad value range. Where I need more darks, or to better define detail, I use a sharper silverpoint tip and work with it linearly, like a pencil.
There are a couple of options for applying pastel dust to the finished silverpoint work. Sometimes I scrape the side of a pastel stick with a straight-edge blade into the well of a watercolor mixing palette. More often now, I use Pan Pastels. In both cases, I dip a dry watercolor brush into the dust and gently apply it to the desired area by gently pushing the strokes into the surface. It takes just a tiny brush-tip full of dust for lots of coverage! Transparent color passages glow on the TerraSkin surface.