The chain is about 5 1/2 inches long. The pendulum bob is about 2 inches long, about 9/16 inches in diameter, and weighs about 15 grams. This would be considered a light weight gemstone pendulum.
The small chamber is about 7 mm (9/32?) diameter and 5 mm high. More space is available in the chamber cap.
The pendulum metal material is nickel plated brass. The chain is also nickel plated brass.
Remember not all gemstones are the same. Expect some slight variations.