One of the mysteries of the English language finally explained.
A tough aggregate of minute, concentrically arranged diamond crystals, occurring naturally in rounded masses especially in Brazil and South Africa, and mined or produced synthetically for industrial purposes.
1930s; earliest use found in Science. From Portuguese balas, ballas, specifically use (although the form with medial -ll- is unexplained) of the plural of bala ball, bullet, with reference to the round shape of the crystal aggregate.
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