Nothing compares to the splendor of ruby stone when it comes to red gemstones. But did you know that spinel, another highly prized gem, fiercely competes with this gemstone king? Do ruby and spinel look same just because of their hue, or are there other commonalities as well? Within the oxide group, spinel comes in a range of hues, including black, red, blue, green, orange, pink, and purple. One of the most vivid and well-known gemstones is red spinel, which resembles rubies. Its chemical formula is magnesium aluminum oxide (MgAl2O4), and it falls within the oxide group. Here, the two differ significantly in terms of their chemical makeup. The Hindi term for ruby stone is Manik, and it belongs to several families of corundum minerals. Al2O3 is the chemical composition of this stone.