Book: Principles of Mining

Overview
Herbert C. Hoover’s 1909 treatise, Principles of Mining: Valuation, Organization and Administration; Copper, Gold, Lead, Silver, Tin and Zinc, distills the practice of mining into an engineering-economics framework intended for both investors and operators. Drawing on global field experience, Hoover argues that success in mining rests less on romance and more on disciplined valuation, cost control, and sound administration. The book’s core message is that a mine is a wasting industrial enterprise whose viability depends on rigorous sampling, sober estimation of reserves, and management systems that convert geologic uncertainty into tolerable business risk.

Valuation and Risk
Hoover places valuation at the center of mining practice. He rejects loose phrases like “ore in sight” and insists on explicit reserve categories anchored in exposure, sample spacing, and geologic continuity. Sampling is treated statistically: many small, representative samples, careful handling to avoid bias, duplicate assays, and the use of averages tempered by probable error. He emphasizes that ore value is an empirical quantity subject to variance, so valuation must assign factors of safety that reflect uncertainty in grade, tonnage, and recoveries. Projection of ore beyond workings must be modest and justified by structure, continuity of mineralization, and verified sampling. He argues that the law of averages governs mining fortunes more than anecdotes, and that professional skepticism is the proper posture toward optimistic projections.

Costs, Prices, and Cut-off
Economic analysis links geology to feasibility. Hoover details unit costs for development, stoping, timbering, hoisting, pumping, power, supervision, and general expense, insisting that smelting charges, freight, treatment losses, and by-product credits be included before any claim of profit. From these, he derives the logical cut-off grade, which varies with costs and metal prices; mining below cut-off is value destruction disguised as tonnage. He is explicit that a mine is a wasting asset: profits are illusory until capital is amortized and provision is made for depreciation and future development. Dividend policy should follow, not precede, demonstrated margins after these charges. He urges sensitivity to price cycles and cautions against building permanent costs on temporary booms.

Organization and Administration
Good mines fail under bad management. Hoover outlines a clear division of authority from board to general manager to underground supervisors, favoring competent, unified technical leadership over committee meddling. He champions systematic reporting, daily tonnage, grade, recovery, and unit costs, compiled into weekly and monthly statements that enable prompt corrections. Incentives should reward output and efficiency without compromising safety or grade control. Procurement, stores, and accounting are to be organized to minimize idle inventory and track cost centers. He advocates steady development ahead of stoping to maintain reserve faces, warning that neglect of development during good times mortgages the future.

Technical Practice and Choice of Methods
Methods must fit the ore body. Hoover surveys development strategies, stoping systems, and the growing role of power, compressed air, and electricity. He stresses ventilation, drainage, timber economy, and the choice between hand and machine drilling as cost questions, not matters of fashion. Metallurgical selection is economic: cyanidation for many gold ores; smelting for copper and lead-silver; concentration for tin and zinc, with careful attention to penalties, recoveries, and transport. He notes the advantages of scale and the gains from consolidating small properties to support modern plants.

Ethics, Promotion, and Due Diligence
Hoover is unsparing about speculative promotion. He urges investors to demand independent sampling, transparent cost estimates, and conservative reserve statements, and to separate exploration capital from dividend expectations. Candor in reports and the avoidance of exaggerated claims are presented as both ethical and economically rational.

Legacy
The book helped professionalize mining by fusing geology with accounting and statistics, shaping modern concepts of reserve classification, cut-off grade, and amortization. Its insistence on measurement, skepticism, and managerial discipline remains a touchstone for mining engineering and resource investment.