Historical clue formulations

• Biotite and lepidolite — 2008-07-18
• Fuchsite and alurgite — 2007-12-28
• Biotite and phlogopite — 2007-09-30
• Certain silicates — 2005-02-13
• Layered minerals — 2003-07-01
• Flaky minerals — 2002-06-17
• They're flaky — 2002-03-23
• They come in sheets — 1999-10-15
• Laminated rocks — 1994-06-10