August Birthstone 2021 – Spinel

Published on: August 4th, 2021

Our previous gemstone-related blog post was all about peridot. If you haven’t read our August Birthstone 2021 – Peridot blog post – please do. This week we continue the conversation on August’s birthstone by talking about spinel. If you are an August baby and/ or have a love for spinel, then this blog post is just for you. Here is everything you need to know about August’s second birthstone, spinel:

About Spinel

Rough Spinel. — **Image Source:** Mindat.org

Spinels are allochromatic gemstones. Meaning that when the mineral is pure, it’s colorless. The colors of spinel are derived from only the presence of trace elements acting as chromophores. Chromium, iron, and cobalt are the most common chromophores in spinel. Spinel comes in a range of colors such as blue, green, red, yellow, black, pink, white, purple, orange, and brown. Spinels are found throughout the world such as Australia, Madagascar, Nigeria, Tanzania, Sri Lanka, Thailand, Cambodia, Vietnam, and Myanmar. Spinel is an 8 on the Mohs scale of mineral hardness. Spinels are durable so should you consider purchasing heirloom jewelry now, spinel could be an option.

Spinel History

The name spinel comes from the Latin word spinner which means thorn. The reason for this name is because the crystal structure of spinel is similar in shape to that of the thorns on a rose bush (as illustrated in the image above).

In the past, it has been said that spinel has been used to help ancient sailors navigate their ships. Sailors as early as the 15th century are believed to have used a form of spinel known as magnetite as a lodestone. This was to magnetize their compasses when they were guarding ships in the night.

It wasn’t until the late 19th century when spinel was recognized as an entirely different gemstone to that of ruby. For example, The Black Prince’s ruby (pictured below) set in the Maltese cross in the front of the Imperial State Crown of the United Kingdom was thought by Henry V to have been a ruby but it is a 170-carat spinel.

The Imperial State Crown of the United Kingdom. (**Image Source:** Royal Collection Trust).

Myth: Spinel can protect its wearer from fire.

Spinel vs Ruby

Red Spinel Ring and Burma Ruby Ring. — Left: Red Spinel Ring. Right: Burma Ruby Ring. (**Image Source:** GIA).

Today, accurate distinctions can be made between spinels and rubies:

Firstly, comparing the two gemstones based on the Mohs scale of mineral hardness. Ruby registers as a 9 whereas spinel registers as an 8. Meaning that ruby is harder when compared to spinel.

Secondly, rubies are dichroic (meaning it shows different colors when viewed from different directions) whereas spinels are singly refractive (it has only one refractive index – like diamonds).

Thirdly, most spinels have the ability to fluoresce in natural daylight but with more of a pinkish hue. Whereas rubies have more of the common bluish hue.