Bonus Question — Low-priced metals: 21-Mat-B1 Hydrometallurgy and Electrometallurgy, December 2014, Q7

Question 7 of 7: Bonus Question — Low-priced metals

Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)

Notes on this paper

Paper format. National Professional Examinations, December 2014 — 10-Met-B1, Mineral Processing. Three hours, closed book, approved Casio/Sharp calculator only. Six numbered Problems (all compulsory except Problem 5) plus a two-mark Bonus Question. Problem 5's rubric asks for any SIX of eleven sketch-and-describe topics; all eleven topics are answered below.

Note on the exam title

Nothing on the paper is a hydrometallurgy (leaching, solvent extraction, electrowinning) or electrometallurgy question; the syllabus actually examined is comminution and grinding-circuit mass balance, particle settling, flotation kinetics, and mineral-processing equipment/terminology — the physical/mechanical beneficiation stage that precedes hydro- or pyro-metallurgical extraction.

Reference texts. The answers below are keyed to the works normally recommended for this syllabus code:

B. A. Wills and J. A. Finch, Wills' Mineral Processing Technology, 8th ed. — comminution and Bond's law (Ch. 6), classification and hydrocyclones (Ch. 9), gravity concentration and jigs (Ch. 10), froth flotation and flotation kinetics (Ch. 12), dense-medium separation and thickening (Ch. 11, 17).
F. F. Aplan (ed.), SME Mineral Processing Handbook — flotation reagents (collectors, frothers, activators), plant flowsheets, comminution circuit design.
A. Taggart, Handbook of Mineral Dressing — classical terminology (probable error, ratio of concentration/enrichment, jig hutch, crusher types).
J. Svarovsky, Solid-Liquid Separation — particle sizing methods, hydrocyclone theory, thickening.

Bonus Question — Low-priced metals (2 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

Around the exam date (December 2014), base-metal cash prices on the London Metal Exchange put several common metals below the USD 1.50/lb threshold, while copper (roughly USD 2.90/lb) and nickel (roughly USD 6.80/lb) were well above it.

Metal	Approx. LME cash price, Dec 2014
$\boxed{\text{Zinc}}$	≈ USD 0.95–1.00/lb
$\boxed{\text{Lead}}$	≈ USD 0.85–0.90/lb

Aluminum (≈ USD 0.80–0.85/lb at the time) is a third valid answer.

Check. This question's correct answer is time-dependent by construction (it asks for the "currently" prevailing price) — the values quoted are approximate historical LME cash settlement prices for December 2014 and are given to establish that zinc, lead and aluminum were the base metals trading below the stated threshold at that time, not as a general or present-day fact.