heart of gold

plural hearts of gold

1. idiomaticA kind, compassionate, or caring attitude; kindheartedness; a person with those qualities.

   Don't let her rough exterior fool you; underneath that grumpy disposition beats a heart of gold.

   2 more examples

   The King's a Bawcock, and a Heart of Gold, / a Lad of Life, an Impe of Fame, / of Parents good, of Fist most valiant:

   1599 (date written), William Shakespeare, “The Life of Henry the Fift”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, [Act IV, scene i]

   "He is modest," said Lady Eglinton, with the air of a proud mother lauding her young offspring. "A heart of gold, my dear Mlle. d'Aumont!" she whispered behind her fan, "under a simple exterior."

   1910, Baroness Orczy, Petticoat Rule

   Antonyms: heart of stone