Historical clue formulations

• Volcanic rock — 2017-03-20
• Pedicurist's stone — 2016-12-06
• Exfoliation tool — 2014-12-28
• Rock that may float — 2013-10-16
• Stone used by pedicurists — 2006-11-12
• Stonelike abrasive — 2006-05-23
• Common exfoliant ingredient — 2005-09-03
• Kind of abrasive — 1995-10-08