What is the meaning of Greenstone?

any of several green-hued minerals used for making various artefacts in early Mesoamerican cultures, e.g. greenschist, chlorastrolite, serpentine, omphacite, or chrysoprase

pounamu, the green-hued minerals of New Zealand used by Māori to make tools, ornaments and weapons (any of three varieties of nephrite jade or one variety of bowenite)

Source: wiktionary.org