True friendship of kindred spirits is rare and precious.
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From 《易经·系辞上》: 二人同心，其利断金；同心之言，其臭如兰 ('When two people share one heart, their force can cut metal; their words are as fragrant as orchids'). 兰 (orchid) became the literary symbol of pure, fragrant friendship.
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Highly literary - you'll mostly meet this in classical poetry, scholarly prose, or Chinese-language tattoo lists. For modern 'close friend', use 知己 or 挚友.
