Asbestos is a fibrous silicate mineral. It is found naturally in the environment. It was mined and made into products by the Romans. The 19th century saw the re-discovery and reintroduction of asbestos and asbestos products. Between 1930 and 1950, many homes were constructed with different asbestos-based materials. This included roofing tiles and floor tiles. The industry continues to produce many chrysotile asbestos materials. The effect of the mining and industrial production of asbestos has been felt in the amount of asbestos-related illnesses. Of serious concern are instances of mesothelioma among asbestos workers. Ignorance of the dangers of asbestos coupled with blatant disregard for human life has resulted in various asbestos cases coming before the courts. Asbestos cases have advanced to different levels of courts as companies fought against the payment of monies for negligence and under other aspects of civil tort law. In the United States the actions taken against W. R. Grace and Company finally ended in 2009 with an acquittal of knowingly harming the people of Libby, Montana. They and other companies, however, have either "voluntarily" or through asbestos cases, paid compensation for those suffering from asbestos-related diseases.