Definition
A low-friction bearing arrangement in which a hardened, sharply pointed pivot rests in a small cup-shaped jewel (typically synthetic sapphire or ruby), allowing a delicate moving element to rotate freely with minimal resistance. In a magnetic compass, the float carrying the compass card is suspended on a jewel-and-pivot bearing so the card can swing freely to align with the Earth's magnetic field.
Plain English
A tiny needle-like point sitting in a small jewel cup, used as a bearing so something can spin or swing very easily. In a compass, it's what lets the compass card turn smoothly to point north.
Context Anchor
Seen in descriptions of the magnetic compass and how the compass card is supported inside the instrument.
Derivation
The name simply describes the two parts: a hard 'jewel' (originally a real gemstone, now usually synthetic sapphire) and a sharp metal 'pivot' that rests in it. Jewels were used because they are extremely hard and smooth, giving almost no friction—which is why the same bearing style is used in fine watches.
Why Pilots Care
Reduces friction so the compass responds promptly and accurately to heading changes instead of sticking or lagging.
Analogy
Think of a sewing needle balanced point-down in a tiny glass cup—almost nothing touches, so it spins with the lightest push. That's the same idea letting a compass card swing freely.
Intuition Check
Jewel does not mean decoration here; it means a very hard, smooth bearing surface. Pivot is the tiny point the compass assembly turns on.
Example Sentence 1
The compass card floats in fluid and rides on a jewel-and-pivot bearing, which is why even a slight bank causes it to swing.
Example Sentence 2
Turbulence can exaggerate heading lag if the jewel-and-pivot bearing has collected dirt or wear.