Supernova (SN) 2014C is unique: a seemingly typical hydrogen-poor SN that started to interact with a dense, hydrogen-rich circumstellar medium (CSM) ~100 days post-explosion. The delayed interaction suggests a detached CSM shell, unlike in a typical SNIIn where the CSM is much closer and the interaction commences earlier post-explosion, indicating a different mass-loss history. We present infrared observations of SN 2014C 1-5yr post-explosion, including uncommon 9.7{mu}m imaging with COMICS on the Subaru telescope. Spectroscopy shows the intermediate-width HeI 1.083{mu}m emission from the interacting region up to the latest epoch 1639 days post-explosion. The last Spitzer/IRAC photometry at 1920 days confirms ongoing CSM interaction. The 1-10{mu}m spectral energy distributions (SEDs) can be explained by a dust model with a mixture of 62% carbonaceous and 38% silicate dust, pointing to a chemically inhomogeneous CSM. The inference of silicate dust is the first among interacting SNe. An SED model with purely carbonaceous CSM dust, while possible, requires more than 0.22M_{sun} of dust, an order of magnitude larger than what has been observed in any SNe at this epoch. The light curve beyond 500days is well fit by an interaction model with a wind-driven CSM and a mass-loss rate of ~10-3M{sun}_/yr, which presents an additional CSM density component exterior to the constant-density shell reported previously in the literature. SN 2014C could originate in a binary system, similar to RY Scuti, which would explain the observed chemical and density profile inhomogeneity in the CSM.