The moonstone / Wilkie Collins.

Enhanced descriptions from Syndetics:

The Moonstone is a stunning yellow diamond the size of a bird's egg that glows like the harvest moon and harbors a flaw in its brilliant depths. Inherited by the beautiful young Englishwoman Rachel Verinder, it is also a sacred talisman to the Hindu priests who hope to bring it back to their holy city in India, from which it was looted long ago. The diamond's disappearance sets in motion an intricately plotted mystery. Wilkie Collins gives the reader all the necessary pieces to the puzzle, but they are so cleverly disguised that his surprise ending takes the breath away.

The elements that make up The Moonstone-- a purloined jewel that carries a mysterious curse, an indefatigable British police sergeant, a drama of theft and murder in a spacious country house--have been repeated, in varying guises, throughout much of the avalanche of detective fiction that followed Collins's immensely popular 1868 novel. But none of those books has surpassed the richness and suspense of the storytelling of The Moonstone , the first detective novel and the continuing standard of its genre.

Introduction by Catherine Peters