“If gold rusts, what then can iron do?”
Source: The Canterbury Tales
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Geoffrey Chaucer 99
English poet 1343–1400Related quotes

Irshadul Qulub; Page 78
Shi'ite Hadith

“Lies are rust on iron. A blemish on power.”
Source: Golden Son (2015), Ch. 15: Truth; Aja

" Statue of Margaret Thatcher unveiled at British Parliament http://legacy.utsandiego.com/news/world/20070221-1456-britain-thatcher-statue.html", Associated Press, 21 February 2007.
On the unveiling of a statue of her in the Members' Lobby of the House of Commons. Baroness Thatcher referred to a previous marble statue which was decapitated http://news.bbc.co.uk/1/hi/england/2091200.stm in 2002.
Post-Prime Ministerial

“As iron is eaten away by rust, so the envious are consumed by their own passion.”
§ 5
From Lives and Opinions of the Eminent Philosophers by Diogenes Laërtius

“Reader, pray that soon this Iron Age
Will crumble, and Beauty escape the rusting cage.”
"Beauty in This Iron Age" in Starlanes #11 (Fall 1953); re-published in Pearls From Peoria (2006)

Antisthenes, 4.
The Lives and Opinions of Eminent Philosophers (c. 200 A.D.), Book 6: The Cynics

“Whom none could overcome with iron or gold.”
Quem nemo ferro potuit superare nec auro.
As quoted by Cicero in De Re Publica, Book III, Chapter IV
Iron is a metonym for sword/warfare, and gold for money/bribery.

“We both know what memories can bring
They bring diamonds and rust”
Diamonds & Rust
Diamonds & Rust (1975)