That my first post : I'll try to follow the guidelines.
1) I provide 2 pictures of my sample : the first one from the tiny green crystals themselves, and the second one from the rock supporting the crystals on its surface.
2) The rock itself is kind of pink or yellow, with tiny dots of black (see pict #2), which may look like mica. Its surface is not polished, but smooth anyway,
because it is very fine grained. One can also notice bright tiny crytals (white ?). It is as heavy as granite.
3) I found it near the riverbanks of Kunene River, downstream of Epupa Falls, on the border between North Namibia and Angola. It was a few hundred meters up the level of the river itself, and does not look like a pebble. It was sitting on top of other rocks, not near any beach, very close to other large blocks of rocks of the same type, and there were several veins of the exact same green crytals visible (about 5 to 10 meters long) on them.
4) the hardness is between 6.5 and 7.
5) Several other pictures that I shot on site are available on request.
Thanks in advance for any help, Regards, Gilbert.