Nakayama is the most famous of the Kyoto tennen toishi mines in part because; of the ancient history surrounding the mine, the previous owners marketing skills, and the extremely fine quality of stones that were dug from that mine site.
Kato-san who owned the mine from the 1920s into the late 1960s stamped some of his stones with his own personal ink stamp while most of the other miners simply wholesaled in bulk their stones with no mine markings or ink stamps to consolidators who marketed them with adorned with their own ink stamps registered by the wholesaler and stamped without regard to mine they originally did or did not came from.
Kato-san evidently was particular about the quality in the stones that he chose to slab up and finish with his ink stampings, and he did not, as a rule release inferior grade stones so in this way his mines reputation was continued on firm footing, not just on myth. Kato-san did however have a method of selling off the bulk of the remainder tonnage through a Take It or Leave It format that was held at the mine area about once a month to a select list of wholesalers. I was told that Kato-san would set up 8 to 10 piles of raw stock assigned to the buyers with a bulk price and they had one chance to buy it. No haggling. If they passed there was a chance that they would not be invited back again anytime soon.
The Nakayama mine was located in on the steep mountain sides at the edges of the town of Takao in the Umegahata valley. The mine site was composed of a series of diggings that followed the desired strata of stone as it unrolled like a ribbon up and over the mountain. The stone found in this portion of the Tamba Terrane was noted for being particularly fine and consistent with even grain and high cutting strength, the ingredients most important to a finishing stone. This is not to say that all of the Nakayama stones are fine and even, but the majority of authentic older stones you will find have a special luxuriant feel and advanced cutting abilities.
The photos below show a selection of Nakayama sharpening stones mined in the mountains above Kyoto in the 1930's. You can see that they came in many colors.
A progression of minerals bound in the binder may run from stone to stone and be displayed as a color scheme. These mineral are independent of the grit or cutting agents inherent to the stone but can be indicative of the hardness or softness of the stone.
Below is a photo of the backs of the above stones.
The kiita or yellow color stones will sometimes have a pattern called nashiji, a form of colored spots that can be darker or lighter than the host stones which resembles a skin of Japanese yellow pear, "nashi" in Japanese.
A close-up photo of an example of the nashijji pattern.
Below you can see a natural circular formation in the strata layers from the honkuchi naori( original formation) from which the Nakayama mine is a part of.
To the left are tomae stones in the asagi catagory tending towards greens. To the right are tomae strata stones that tend more towards blue to blue-gray, some call these mizu tomae. Mizu is water.