Definition
A low-friction bearing arrangement in which a hardened, polished pointed pivot rests in a small, smooth, jewel-like cup, allowing a delicate moving part to rotate freely with minimal resistance. In the magnetic compass, the float that carries the magnets is suspended on this type of mounting so it can swing easily and align with the Earth's magnetic field.
Plain English
A tiny pointed shaft sitting inside a small polished cup, used so the compass card can spin almost without friction.
Context Anchor
Seen in magnetic compass construction when describing how the compass card is supported inside the compass case.
Derivation
The 'jewel' refers to a small piece of hard, polished material (historically a real gemstone such as sapphire, used in fine watches) shaped into a tiny cup. The 'pivot' is the sharp, hardened point that rests in that cup. Together they form a bearing that turns with very little drag, which is why this design has been used for centuries in precision instruments.
Why Pilots Care
Friction-free rotation lets the compass respond accurately and quickly to heading changes without lag or sticking that could mislead the pilot.
Analogy
Think of a spinning top balanced on its tip inside a smooth dimple -- it can turn easily because almost nothing is touching it.
Intuition Check
Do not read “jewel” as decoration here. In this context, the jewel is a hard bearing surface that helps the compass move smoothly.
Example Sentence 1
The compass card is suspended on a jewel-and-pivot type mounting so it can rotate freely and align with magnetic north.
Example Sentence 2
Pilots confirm the jewel-and-pivot type mounting is intact during compass checks because any binding would produce unreliable readings.