What compound did the Curies separate from a tonne of pitchblende in 1902?

The Curies separated radium chloride from a tonne of pitchblende in 1902.

Pitchblende, also called uraninite, is a uranium ore. After removing uranium, Marie and Pierre Curie found that the residue remained intensely radioactive. Radium was chemically similar to barium, so isolating it required repeated dissolving, concentrating, and differential crystallization of enormous quantities of material. From one tonne of pitchblende, they obtained only about one-tenth of a gram of radium chloride.

The compound was not pure radium metal. Radium chloride was a salt that could be handled and further purified; in 1910, Marie Curie and André-Louis Debierne used electrolysis of radium chloride to isolate radium metal. Another common mix-up is polonium: the Curies announced polonium in July 1898, while radium was announced in December 1898. The arduous separation work demonstrated that the new element was real and helped make radioactivity a serious subject of chemical research.