Assertion: chrome tourmaline | /r/HasProperty | quite a rare material
Facets:
Source sentences:
text: Chrome tourmaline was first mined in Tanzania in the 1960s and is quite a rare material.
text: One particularly beautiful variety is chrome tourmaline, a rare type of tourmaline from Tanzania which occurs in a very rich green color caused by chromium, the same element which causes the green in emerald.