From General Statement Purpose of the Report: "The present investigation was undertaken for the purpose of supplying some of the material so badly needed in the valuation and more efficient operation of oil properties. Because of the lack of time for further studies, the amount of data already accumulated and the policy of the Bureau of Mines of publishing as soon as possible any information that may be of use to an industry, the bulletin is issued now."

From Introduction: "Vocalization in retorts has been, until recently, the only commercial process of producing spelter, hence the zinc mine operators have had to meet the terms of the zinc mine operators have had to meet the terms of the zinc smelters in regard to the following requirements: (1) Minimum percentage of zinc the ore must contain; (2) the chemical combination of the zinc in the ore; (3) the proportion present of those elements that interfere with the successful recovery of the zinc when the ore is retorted. As stated previously, and as will be shown later, a large part of the valuable mineral content of the ore is lost in effecting this concentration. As a result of the other requirements that have to be met in zinc smelting, much zinc is lost in the mining and milling of zinc ore."