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C-2017 K2 is intrinsically the brightest Oort cloud comet found in recent history comma and presents a unique opportunity to efficiently characterize the constituent properties of a still primitive comet on its way in toward the inner solar system for the very first time. Its exceptional brightness in the outer solar system suggests it to be much larger than typical Oort cloud comets---normally too faint to observe at these distances---and makes it a particularly compelling target for early polarimetric characterization comma which requires a high signal-to-noise ratio to usefully constrain its dust properties. Imaging polarimetry of nearby comets has previously revealed varied polarized structures comma such as halos and jets comma that reflect spatial variation in grain size and structure. Jets are of particular interest as they entrain and expose fresh grains from beneath the surface comma previously shielded from the space environment since the formation of the solar system comma and are too small-narrow to be resolved in the outer solar system by ground-based imaging polarimetry. We propose to use high resolution HST-ACS polarimetry and color imaging of C-2017 K2 at a pre-perihelion epoch 6.5--7 au from the Sun comma well before the onset of water ice sublimation comma to constrain the properties of refractory grains in the jets and surrounding coma comma and their physical evolution as they move outward from the nucleus. These observations comma in concert with analogous results from more evolved comets in the inner solar system comma will probe the formation environments and evolutionary histories of these assorted comets comma and their implications on the formation and evolution of the solar system as a whole.