How can I create a glass globe with a sandblasted effect? I have set myself a challenge to create a glass globe with sand blasted land mass and totally transparent sea.

Creating the globe is straight forward enough but I'm not sure of the best way to create the land. I've tried adding a UV map but the glass always becomes solid even where the sea is...

Can anyone suggest the simplest way to do this? Or, better still, an example for creating a sandblasted effect on glass.
Find or create a black and white texture which separates the parts you want to be "sand-blasted" from the parts you want smooth. For example, this public-domain land-mask from here.

Open the mask image in a texture node. Plug the generated output of the texture coordinate node into the vector input of the texture node, and set the image node's projection to Sphere.
This avoids the need for a UV map, and prevents artifacts near the poles.

Plug the texture into the roughness output of a glass shader, optionally using a mix node to adjust the min and max roughness: