Top 10 Gemstones with a Hexagonal Crystal System

Metal_Treasure
The hexagonal system gives the crystals six sides. Three of these are equal in length and meet at 60° to each other. The C, or vertical axis, is at 90° to the shorter axes.

Mineralogists sometimes divide the hexagonal crystal system into two systems based on their external appearance - the hexagonal and the trigonal. But the trigonal crystal system is a subsystem of the hexagonal and most gem references will list the trigonal system as hexagonal.

The Top Ten

1 Taaffeite Taaffeite

There were images to these items... Why they suddenly disappeared? - Metal_Treasure

Clearly a Hexagonal Crystal Subsystem. It's visible - Metal_Treasure

Pretty. - Not_A_Weeaboo

2 Beryl Beryl

Hexagonal subsystem, obviously. It's also visible.
The image shows Red Beryl, which is the rarest color for beryl, but beryl is usually colorless - Metal_Treasure

3 Ruby

Its crystals have a Trigonal shape, so it's Trigonal subsystem of the Hexagonal system - Metal_Treasure

4 Aquamarine Aquamarine

It belongs to the Hexagonal subsystem because aquamarine is just blue beryl and all beryls are with Hexagonal shapes - Metal_Treasure

5 Sapphire Sapphire

Trigonal subsystem (the image shows black Sapphire but they can occur in all colors except red) - Metal_Treasure

6 Emerald

Hexagonal subsystem - because Emerald is actually deep green beryl - Metal_Treasure

7 Benitoite Benitoite

Hexagonal subsystem.
Its blue color is awesome (color isn't related to the crystal system though) - Metal_Treasure

8 Tourmaline Tourmaline

Trigonal subsystem (the image shows Green Tourmaline - green is the classic color of the gem, but they can be different colors) - Metal_Treasure

9 Morganite Morganite

Hexagonal subsystem because it's pink beryl - Metal_Treasure

10 Amethyst Amethyst

Trigonal subsystem (amethyst is a semi-precious variety of quartz ) - Metal_Treasure

The Contenders

11 Jeremejevite Jeremejevite

One of the rarest gems in the world - Metal_Treasure

12 Citrine
13 Poudretteite Poudretteite

Another extremely rare gem first found in Quebec, Canada - Metal_Treasure

14 Musgravite Musgravite
15 Sugilite
16 Hibonite Hibonite
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