Mineralogical variations within the Bloom Lake iron ore deposit


Hugues Longuépée, Champion Iron Mines

Like in all the iron mines of the Fermont-Labrador City area, the Bloom Lake ore is a mix of hematite and magnetite.  What sets the Bloom Lake Mine apart is the proportion of silicates that is currently included in the reserves and the hematite-to-magnetite ratio that varies from 0 to more than 80.  Changes can be seen over a short distance, from one end of the mine to the other.  The Bloom West pit is composed of an almost-pure hematite ore with an average of less than 1% magnetite and little silicates while the Chief Peak pit to the east is more of a magnetite-silicates ore.  The silicates are actinolite, grunerite, cummingtonite, hornblende, augite and enstatite.  Goethite is also present in some area of the mine. The variability in mineralogy and texture represent a challenge for mine’s operation and concentration plant as it has a direct impact on iron recovery.  To help plan a more efficient blend and constant quality of the product through the life of mine, geologists have put together a series of geochemical tools that help differentiate the different types of ores that have been described by different geologists throughout the deposit’s history. The talk will review the overall geology of the deposit with a focus on the spatial distribution of the different ores and how to recognize the mineral assemblage using chemistry from drill core and drill cuttings.
Keywords: Bloom Lake, Mineralogy, geology