24-MMP-A1 General Geology and Exploration · December 2018
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Mining and Mineral Processing Engineering, 09-MMP-A1 General Geology and Exploration, 2018-Dec. Closed book; only a Casio or Sharp approved calculator permitted. Questions 1–4 are compulsory; a candidate then completes ONE more question chosen from Questions 5, 6 or 7.
Reference texts: Klein & Dutrow, Manual of Mineral Science, 23rd ed. (crystal systems, diagnostic physical properties, hand-specimen identification); Guilbert & Park, The Geology of Ore Deposits (genetic classification, deposit-type descriptions throughout); Evans, Ore Geology and Industrial Minerals, 3rd ed. (deposit classification, structural controls on ore); Telford, Geldart & Sheriff, Applied Geophysics, 2nd ed. (gravity, magnetic, electrical, EM and seismic methods); Rose, Hawkes & Webb, Geochemistry in Mineral Exploration, 2nd ed. (sample-medium selection, dispersion patterns); Peters, Exploration and Mining Geology, 2nd ed. (drilling methods and sampling).
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.
The five minerals are compared directly in the table below, since parts (a), (b) and (c) each ask the same question of every specimen.
| Mineral | Streak colour | Major ore element | Diagnostic physical property |
|---|---|---|---|
| (i) Galena, PbS | Lead-grey to black (metallic) | Lead (Pb) | Three perfect cleavages at 90° (cubic cleavage) combined with very high density (≈7.5) for a mineral this soft |
| (ii) Cassiterite, SnO₂ | White to pale grey or pale brown – distinctly lighter than the mineral's own brown-to-black body colour | Tin (Sn) | Exceptionally high density (≈7.0) combined with adamantine lustre and hardness 6–7, unusual for an oxide this dense |
| (iii) Scheelite, CaWO₄ | White | Tungsten (W) | Bright blue-white fluorescence under shortwave ultraviolet light – the classic field test used by prospectors |
| (iv) Sphalerite, ZnS | White to pale yellow-brown – again much lighter than the mineral's own colour | Zinc (Zn) | Resinous lustre with six directions of perfect dodecahedral cleavage |
| (v) Ilmenite, FeTiO₃ | Black to brownish-black – unlike (ii) and (iv), the streak matches the mineral's own dark colour | Titanium (Ti) | Weakly magnetic (attracted to a hand magnet only weakly, unlike strongly-magnetic magnetite) with a submetallic lustre and black streak |
The streak column is the most diagnostic single test here: cassiterite and sphalerite both look dark in hand specimen but streak almost white, immediately separating them from genuinely metallic, dark-streaking minerals such as galena and ilmenite. Ilmenite's WEAK magnetism (as opposed to magnetite's strong response) is the property most often confused in the field, and is why it is always tested against a known magnetite specimen rather than judged in isolation.
Excluding galena, cassiterite, scheelite, sphalerite and ilmenite, one representative ore mineral for each element is:
| Element | Ore mineral | Formula |
|---|---|---|
| (i) Mercury (Hg) | Cinnabar | HgS |
| (ii) Cobalt (Co) | Cobaltite | CoAsS |
| (iii) Iron (Fe) | Hematite | Fe₂O₃ |
| (iv) Manganese (Mn) | Pyrolusite | MnO₂ |
| (v) Aluminum (Al) | Bauxite (an ore rock, not a single mineral) – principally the mineral gibbsite | Al(OH)₃ |
Aluminum is the deliberate exception in this list: unlike the other four elements, there is no single dominant aluminum ore mineral analogous to cinnabar or pyrolusite – bauxite is a residual weathering-product ROCK made of a mixture of aluminum hydroxide minerals (gibbsite, boehmite and diaspore), which is why economic geology texts always describe it as an ore rock rather than an ore mineral.
