The ring silicates are complex in structure. I struggle to understand them and wouldnt begin to try an explanation. But the minerals that fall under this category are well known for their beauty: tourmaline and beryl.
Tourmalines are found in pegmatites and are often treasured as gemstones, in particular the ones of which the chemical structure has changed during the formation, resulting in many colors. I sold green tourmaline points in my shop for a while and they were tremendously popular.
Beryl in its transparent form is highly valued as emerald, aquamarine, and heliodor. Its typical crystal form is a six sided prism.
Cordierite has the same structure as beryl but a different chemical composition. It resembles quartz. It doesn't fracture easily during heating and cooling and is therefore valuable as a refractory.
Miserable cold and rainy today.