By 2005, the residual radioactivity had declined to 4,800 curies. By one estimate, the river contains 120 million curies of radioactive waste. During this accident some 10,000 curies or 370 TBq of radioactive material was released. This spurred the Curies to search for additional radioactive elements. The Curies undertook the arduous task of separating out radium salt by differential crystallization. Three radioactive minerals are also named after the Curies&colon; curite, sklodowskite, and cuprosklodowskite. A few curies of Po emit a blue glow caused by excitation of surrounding air. The Sabines were integrated into the existing tribes and curies. In 2007, a metro station in Paris was renamed to honour both of the Curies. The award money allowed the Curies to hire their first laboratory assistant. Florence accepted an inscribed book from the Curies, breaking her informal rule against autographs. This made the Curies the family with the most Nobel laureates to date. The Curies, however, did not predict the converse piezoelectric effect. The Curies announced their discovery to the French Academy of Sciences on 26 December 1898. The Curies did not patent their discovery and benefited little from this increasingly profitable business.