Granite is able to “float” quite nicely on the surface and is an excellent insulation so we do have some very ancient crust available but nothing but zircon contained in slightly younger sentiment or granite. So we only can model much of the Hadean crust. The ancient plutons found on North America and, particularly South Africa and Australia get you evidence of almost water like lava, kimberlite pipes and nickel deposits from before the core had assumed all its current form. I’d love to go and have a look.
Yeah, it would be very cool go and see all that first hand... Very cool indeed!
If I am remembering right, I think that they believe that those kimberlites are from the middle to lower mantle, not the core area. And they wouldn’t be from before the core was formed, as it was formed 30-50 million years after the formation of the solar system/earth, predating the oldest rocks and these rocks in particular by many millions to billions of years. The ages of emplacement of the south african kimberlites is approximately 120 million years BP and the australian ones 1.2 billion years BP.