Macro-pinacoids Small 320×316 Medium 640×631 Large 1024×1010 Download Tiff Original 2400×2368 | (308.8 KB) Description Principal forms of the triclinic system: macro-pinacoids Keywords geology, macro-pinacoids, triclinic forms Galleries Prisms Source: Amadeus W. Grabau A Textbook of Geology (Boston: D.C. Heath & Co., 1920) 48