Historical clue formulations

• Like obsidian rock, once — 2026-07-23
• Like metal before die casting — 2019-03-02
• Like lava or magma — 2017-11-01
• Like the outer core of the earth — 2016-10-28
• Not yet hard — 2010-02-10
• Liquefied — 2009-02-01
• Not hard — 2005-10-15
• Like the golden calf — 1999-06-26