Well, let me calm your fears. I have spoken to people who know. They have been to the source and spoken to the people at Imyres (the company that produces Grolleg).
Nothing has changed about Grolleg.
They have not changed to a new mine. They are not discontinuing the product. Nothing in the slightest has changed. Imyres claims to have a 25-30 year supply of Grolleg. Enough to keep all of us making for a good long while.
The ceramics world is full of a lot of rumors. People love to chat and that is great. We need communication and the dissemination of information. But, we also need to watch the rumors that we spread. I have had people ask me, bordering on a panic about this situation. This is not helpful. If you hear something that may be fatalistic, don't go spreading it around until you have attempted to check a few sources.
It is true, materials do change and are discontinued. Kona F4 is gone. G200 feldspar is now G200hp and has a slightly different composition. Gerstly Borate is... well hell, even I still have no idea what is going on with Gerstly. As I understand it, it is still available for purchase. Materials will come and go, that is the way it has always been. I collect a lot of glaze recipes here in Alfred, and the fact is, I stop when I get to formulas that pre-date the mid-80's because there was a major material shift around that time.
It is true, there is an unfortunate disconnect between producers and users in the ceramics world. The statement that the material producers don't care about us is true. We are a minute portion of their business. But that does not mean that the information is unavailable to us.
So everyone stay calm. If you have questions, please ask. Hopefully together we can spread useful information.