[tshadley]

Earth's crust: not quite the same as Cu/Zn but way more than I expected:

https://periodictable.com/Properties/A/CrustAbundance.an.htm...

Lithium: 0.0017% Copper: 0.0068% Zinc: 0.0078%

Seawater: https://sciencenotes.org/abundance-of-elements-in-earths-oce...

Lithium: 0.18 mg/L