K.R.P. acknowledges support from a National Science Foundation Graduate Research Fellowship and a National Defense Science and Engineering Graduate Fellowship from the Department of Defense. N.V. acknowledges funding from the Leopoldina Fellowship Program. M.K. acknowledges support from the Alexander von Humboldt Foundation. C.C.P. acknowledges the support of an Edward, Frances and Shirley B. Daniels and Wyss Fellowship while at the Radcliffe Institute for Advanced Study (2012−2013). The authors thank Dr. Ian Burgess and Dr. Caitlin Howell for helpful discussions and Grant England and Jack Alvarenga for help with the angular reflectance and infrared instruments, respectively. This work was funded with support from the Air Force Office of Scientific Research (AFOSR) via Grant FA9550-09-0669-DOD35CAP. This work was performed in part at the Center for Nanoscale Systems (CNS) at Harvard University, which is supported by National Science Foundation Grant ECS-0335765.