Pure Ice and Frozen Fossils

Pure ice would be a transparent version of the ice blocks.
It could only be mined with a pickaxe with the Silk Touch effect.
It would be slippery than a regular block of ice.

It would only appear as part of a new structure, the Frozen Fossil. These are new fossil variants that representing a huge aquatic creatures.
These fossils would be made up entirely of blocks of bone and would be completely surrounded by Pure Ice, making them appear frozen for centuries.

They would appear as part of the icebergs in the Frozen Ocean and less frequently in caves beneath snow biomes.