First let me say I do not think these are rubies, they are more the color of pink sapphires. A pink sapphire is technically a ruby, that did not get red enough but stayed pink. I love this ring, it will stay in my personal collection for sure. It is sterling silver, featuring a 5mmx4mm oval natural Alexandrite gemstone.
Alexandrite, is one of the rarest, and most expensive gemstones in the world. Named after Czar Alexander the Second, it was found in the 1830's in the Ural Mountains. It is a phenomenon gemstone, as it is a color change gemstone. A good Alexandrite will be emerald by day, and ruby by night. The thicker the stone, the better the color change usually is. The Ural mine has been mined out completely, but Alexandrite can also be found in India, Brazil, Tanzania, Madagascar, and Burma. It has a hardness of 8 1/2 on the Moh's hardness scale so it is a durable gemstone. However, it is sensitive to knocks, and dings, and color change to the stone can occur if exposed to extreme heat.
Since my kids birthstones are both a ruby, and an emerald, this is a perfect mothers stone for me. I got both in one stone. I have another one, that is just slightly smaller, and the color change weaker, but it is still a lovely stone. I have not decided what to set it in yet.