Soru

To isolate zircon crystals from a granite sample for uranium-lead geochronology, geologists follow a rigorous multi-step physical and chemical separation protocol. First, the bulk granite is reduced to a fine powder using a jaw crusher followed by a disc mill, ensuring the grain size matches the expected size of individual zircon grains without fracturing them. Next, the resulting powder is passed through a wet-shaking Wilfley table, which uses water flow and density differentials to separate lighter quartz and feldspar from the heavier mineral fraction. Before the remaining heavy concentrate can be subjected to magnetic separation, it must be thoroughly dried in an oven. Once dry, the sample is passed through a hand magnet to extract highly magnetic magnetite, and subsequently processed through a Frantz isodynamic separator at progressively higher electrical currents to isolate weakly magnetic minerals like biotite and hornblende from non-magnetic zircon. The non-magnetic residue is then immersed in methylene iodide, a heavy liquid with a specific gravity of 3.3, allowing the denser zircons to sink while any remaining lighter minerals float to the surface. Finally, the recovered zircon fraction is hand-picked under a binocular microscope to select high-quality, inclusion-free grains for mass spectrometry.

Based on the geological sample preparation protocol described in the passage, which of the following lists two actions that must both be completed before the non-magnetic zircon can be separated from weakly magnetic minerals like biotite and hornblende?