Koetsu cartridges. They must be something special.

Jason, I just read the long piece on "pickups" in Wikipedia.  Seems there are a few different types and they operate in a few different ways, any set of which could affect the recorded signal in one way or another.  So I would guess it is about as difficult to say what the type of magnet does to the sound from a pickup as it is to say how the magnetic material of a phono cartridge affects its sound.  I am not saying there is no effect; I am only wondering how one would know or how to investigate that effect as an isolated factor.

Given that Koetsu was a family business and its only emplyees were Sugano San the elder and his son who are both now deceased, but nobody else:

Anyone who manufactured cartridges for Koetsu must be manufacturing them from beyond the grave.

One observation for which I don't have an answer- the Jade sounds different than the Tiger Eye on the same system. From what I gather the innards of both cartridges are the same. The difference in the hardness of the stone is recognized, generally (you can look it up under the Moh Scale for each). I don't know how much that contributes-- neither stone absorbs resonance in the same way that something like wood would; and there was the myth that the better motor assemblies were reserved for the upper tier Koetsu but I think its just that, a myth. 

I will probably try Ana Mighty in France when I'm due for a retip; I gather they had some history with Koetsu back in the day. Those Medialux articles posted upstream are a pretty good introduction to the product line; sadly, the company is no more, though I understand why the family opted not to "sell the brand" to a 3rd party-- it would not have been the same. 

It might've been even better, and that's not what they wanted.

I like the sound of the stone-body Koetsus.  Most of my friends who own or are familiar with the lineup prefer the Rosewood Signature Platinum.  It is a matter of personal preference.  Regardless of the science, the cartridges sound a little different.  But, I suspect, a choices made between the types of stone-body cartridges is primarily based on appearance.  I have seen most of the types, and my favorite look is that of the Blue Lace.