Carrie Jane Billings Everson discovered, tested, and proved a method for bulk oil flotation concentration of mineral ores, the precursor to modern froth flotation methods of minerals concentration. She patented her process in 1886. Carrie Everson performed her pioneering work at bench scale. In the early 1890s, co-workers built and operated demonstration plants incorporating her bulk oil flotation process. However, mining companies at the time paid little attention to her work.
Carrie Everson's 1886 patent reads: "The discovery which forms the basis of my invention is that metals and metallic substances in a comminuted state will unite with compounds of fats or oils and acids, and that such compounds will not unite with comminuted quartz or other rocky gangue." She states with some assurance, "If my invention is inapplicable to any particular rocky ores or class or classes of rocky ores, or to the concentration of any particular metal, such limitations are not now know to me."
A subsequent paragraph reads: "Among the ores upon which I have operated successfully by means of my invention are the following: Ores containing native gold and silver, kerargyrite, argentite, argentiferous galena, and a variety of double and otherwise compound sulphides of silver, with copper, antimony, arsenic, and other base-metal sulphides...I have also operated successfully upon ores containing tellurides of gold, silver, and lead, and upon others containing the oxides and carbonates of copper and the carbonate of lead. All the metals or metallic mineral portions of these ores are acted upon by the admixture described, in such manner as to permit the rocky gangue to be removed by a washing process, after which several metals may be separated by the usual means."
Carrie Everson's patent expired before she had the opportunity to enjoy the benefits of her invention. In 1916, her son, John L. Everson, wrote in "The Mining American": "For several years previous to her death, she was aware that her inventions were being successfully employed but her only comment was that she was glad to know that, at last someone was to derive benefit from her discoveries."
Carrie Billings was born in Massachusetts, grew up primarily in Illinois, and received an excellent education. She married a physician, William K. Everson, in 1864. As Carrie Everson, she became a self-taught chemist and inventor, whose investigations into extractive metallurgy in the late 1870s were prompted by a failed family investment in a mining property. This work led to her 1886 patent. A shared patent for a dry flotation process obtained in 1892 and a variety of other inventions not related to mining testify to Carrie Everson's rare inventive talent.