Gizmodo has a cute story -- Why Mathematicians Are Hoarding This Special Type of Japanese Chalk. Apparently, the firm that made these chalks is no more.
3. So what is the best chalk out there?
I have wrestled with this question and spent a bit of time pursing this over my sabbatical last year. There have been rumors about a dream chalk, a chalk so powerful that mathematics practically writes itself; a chalk so amazing that no incorrect proof can be written using this chalk. I can finally say, after months of pursuit, that such a chalk indeed exists. It is called the Hagoromo Fulltouch Chalk.
For those lucky few who have used it, it can truly be called the Michael Jordan of chalk, the Rolls Royce of chalk. [Bold emphasis added]