The U.S. Supreme Court case Minerals Separation, Limited et al. v. Butte & Superior Mining Company, also known as Butte & Superior Copper Company, Limited in 1918 revolved around a patent dispute over the process of extracting copper from its ores using oil froth flotation method. The plaintiff, Minerals Separation Ltd., claimed that the defendant had infringed upon their patented process by employing a similar technique for ore extraction without permission or license to do so. However, the defendant argued that they were not infringing because their method was significantly different and more efficient than what was described in the plaintiff's patent claim. In reviewing this case, the court examined whether there was an infringement based on how closely related both methods were and if any improvements made by Butte & Superior constituted a new invention altogether or just minor adjustments to an existing one. Ultimately, it ruled in favor of Minerals Separation Ltd., stating that even though there might be differences between both processes due to improvements made by Butte & Superior Mining Co., these did not change fundamentally how copper is extracted from its ores using oil froth flotation - which remained at heart of both techniques thus constituting an infringement.

The dissenting opinion in the case of Minerals Separation, Limited et al. v. Butte & Superior Mining Company argued that the patent granted to Minerals Separation was invalid because it lacked novelty and inventiveness, key requirements for a valid patent under U.S law. The justice believed that the process patented by Minerals Separation - using oil to separate valuable minerals from less valuable ones - had already been used extensively before their supposed invention. Furthermore, they argued that even if this method hadn't been previously used exactly as described in the patent, it would have been obvious to anyone skilled in mineral separation techniques at the time and thus not worthy of a patent grant. They also pointed out inconsistencies between what was claimed in the original application and what was eventually patented which further undermined its validity.