Uranus is the seventh planet from the Sun and an ice giant, composed of water, ammonia and methane. It’s the coolest planet in the solar system (−224 °C), and takes 84 years to orbit the Sun. It has a ring system, 28 satellites, and a peak wind speed of 900 km/h. Definitely not a place to go hang-gliding.

The orb is made of Green Quartz. Coming in many different shades, depending on what contaminant is in it (iron, copper, etc.), Quartz is a ubiquitous part of our planet’s geology, being a constituent part of igneous rocks, and most beaches! Green Quartz is the result of ionising radiation and heat, and is mainly mined in a small location in Brazil.

Venus is the second closest to the Sun, and a planet of extremes. Its dense atmosphere creates a surface level pressure 92 times that of Earth, and it’s a cocktail of carbon dioxide and sulphuric acid, all heated up to a balmy 464 °C… Its year is 224.7 days long. Amazingly, it’s possible that life may exist there, as temperatures in the clouds are only 40-70 °C, meaning that extremophile microorganisms may live there, however unlikely.

As you can see in the gallery below, there’s a huge variance between the planets, as there should be, and they do a good job interpreting their respective worlds. Remember, each of these is unique, and shaped from a natural mineral, so no two Jupiter coins, for example, will be identical, adding to the attraction of them.

The packaging looks first class, and custom-made for the task. Clearly, this series is a labour of love at Mint XXI, and they have a fine history with large series like this, including Greek Mythology, and the Way to Valhalla, amongst others, so it’s in safe hands. As we said, the base coin doesn’t exhibit much variety, but this release is more about the whole thing than on any part of it, and on that score, it looks to be a huge success, one the astronomy crowd would love to have on display, as would former stonemasons/geology nuts like myself. Available now, each issue has a mintage of 500 pieces.