In certain lighting conditions, silk produces a shimmering optical effect, which is due to the triangular prism-like structure of silk fibers. These prisms reflect light at various angles, which results in the subtle rainbow hue that has made silk so famous. You can also try your hand (literally) at freehand https://www.catawiki.com/en/l/85648163-silk-bedspread-225-cm-195-cm-silk-damask