Here’s a great deep blue aqua from Namibia. The c axis is open with the top section being almost completely transparent. The color deepens significantly further down and there’s a bit of matrix along the back and bottom shown in the image. I love the tiny penetrator along one corner of the termination.
It measures 44 x 16 x 15 mm and weighs 16.8 grams
https://youtu.be/Ayw_QoXSW2w