Historical clue formulations

• Element of some chips — 2020-01-23
• Element in chips — 2014-02-12
• Element used to make semiconductors — 2012-04-23
• More than a quarter of the earth's crust, by mass — 2012-01-22
• More than a quarter of the earth's crust — 2011-04-15
• ___ Valley — 2010-11-24
• Element used to make semiconductors — 2008-05-23
• Element used to make semiconductors — 2004-08-21
• ____ Valley — 1995-07-20