Unlike the cubic system crystals in the trigonal system show doubling, meaning that the light inside the crystal visibly splits into two directions.

Rubies do grow in a hexagonal shape too, but it is usually flat and shallow. Corundum is a little more complex and falls into the trigonal crystal system, growing in a spindle shape. Diamonds have a very simple structure and fall into the cubic crystal system, growing in a bi-pyramidal shape (the Black Prince Ruby shows this growth habit too). Corundum is made up of multiple elements, aluminum and oxygen ( Al2O3), and is also colored by various trace elements.īecause of how these elements react to one another, they form different crystal structures. Diamonds are generally pure carbon with extremely small amounts of trace elements that can cause other colors in them, mostly nitrogen causing a yellow color. The most basic difference between corundum and diamonds is their chemistry. This makes the following examples of finely colored diamonds exceptionally rare. Unlike sapphires and rubies, colors other than yellow and brown in diamonds are very rare, accounting for less than 2% of all diamonds. This is where the similarities end though, starting with the fact they are colored by different elements. Like how corundum comes in the full rainbow of colors between its ruby and sapphire varieties (including colorless), diamonds can come in colors other than colorless like green, yellow, blue, and very rarely, red. It currently sits in the imperial state crown of Britain, front and center. Despite the title of “ruby” (a variety of corundum) the ruby is actually a piece of spinel. Any blue, transparent stone was a sapphire, any red stone was a ruby, anything green and clear, an emerald, etc.Īmongst the most famous examples of this mix-up is the Black Prince Ruby. Going back to antiquity, there was no distinction between gems of the same color. These gemstones have a long history of being confused for one another. Rubies from Sri Lanka (formerly Ceylon).Differences Between Diamonds and Corundum.Differences Between Rubies and Other Gems.Calculating the Cost of a Ruby Engagement Ring.

Corundum ruby sapphire