A vacuum insulated panel (VIP) and a method of manufacturing a VIP includes a rigid core material having high insulation and low conductivity properties. The rigid core may be made of an inorganic material that effectively mimics a porous silica core material. The core material includes large particles of an inorganic material having a diameter in a range of 10 μm to 50 μm. A portion of these large particles may be ground into small particles having a diameter of less than 1 μm. The small particles are mixed with a portion of the large particles to form a core material which is then mixed with a fiber skeleton and compacted under vacuum along with a fibrous skeleton for structure. The resulting structure provides a porosity ranging from 10 nm to 1 μm in diameter.