The Invitica are similar to the translucent Arkansas I own in hardness [knife test], they are technically a novaculite stone and grade about 2.5 SG. They have a light translucent glow near the cut edge.
Water stones; similar to Japanese hones, they have about 60% novaculite and the sedimentary binding although hard, does produce slurry. These from a high medium grade to finishing grades, also. These are Lochinvar, Perisa & Saint Luke’s Quarry in the listings.
The Rosetta range in fineness from an unglazed ceramic to a tight & dense type and are then for burnishing. They have many variations in the binding sediment producing a number of actual differences in color. The matrix are quite high in sediment and are more porous, still more for high carbon alloys as opposed to straight razor types.
The Nakoda are a novaculite stone, quite brittle and a high end straight razor type for finishing. In a sense, they granulate more readily than Invitica and produce off white to amber slurry.