Japanese chalk brand Hagoromo is not just any other chalk. Preferred by top-notch mathematicians across the world, Hagoromo has been addressed as the “Rolls Royce of chalks” and the “Michael Jordan of chalks”. One mathematician jokingly says that he assumed the special ingredient in Hagomoro’s Fulltouch chalk was “angel tears”.

Hagomoro shut down in 2015, but before it went out of business, professors and mathematicians stocked up on supply, with some having enough chalk to last them ten years. The news of Hagoromo’s closing operations was referred to as chalkapocalypse, according to Brian Conrad, a mathematics professor at Stanford University. The formula of Hagomoro chalk was eventually bought and reproduced by a Korean company.