BTW, what is the difference between ebonite and vulcanite?
Ebonite and vulcanite are used pretty much interchangeably to mean "hard black rubber". However, in pipe making circles, there's a huge difference between the two.
Ebonite is a higher quality material that's lower in sulfur. It is harder than vulcanite, and easier to machine. It also has, when manufactured correctly, a much lower incidence of inclusions or bubbles in the material. It's furnished in rods of one meter (only manufacturers I know of are in Europe) and it comes in sizes from a couple mm all the way up to 50mm.
Vulcanite is a much softer rubber, having a much higher sulfur content. It is typically used only to make pre-molded stems or gee-gaws since the softer rubber can flow into the small areas of the molding press more readily. Bubbles are common, and a wide variance in batch quality also.
The most imnportant thing is that, because ebonite has less sulfur and other additives, it takes a much longer time to oxidize. Both will eventually oxidize, losing their shine and going a strange color anywhere from olive green to ugly gray, but the high quality ebonite will stay black considerably longer.
As far as the swirled stuff mentioned above, I'm the one coordinating the group buy on pipemakersforum.com. It's not really off the ground yet (we pipe smokers are a patient and methodical bunch) but it's on the horizon. We just completed an ebonite buy where we reached well over the minimum order amount, and any day now I'll be drowning in rod that needs to be shipped out.
These types of buys are fairly regular on the pipe makers forum, and if there's any interest I can post a heads-up here when we have a go at the next one.
And, of course, since I'm a pipe maker, I have loads of this stuff on hand. If you're in desperate need of a piece for a pen, send me an email. I posted some pen blanks of ebonite on eBay a while back, but only had one taker in the 5 weeks or so I had them listed. That pretty much sealed it for me, since that ate into all the profit I might have made, so I never relisted them.