A specimen hosting several rather large clusters of dark green and lustrous clinoatacamite set against a contrasting quartz-lined vug.
On an absuloute scale, this is probably the third best in the lot, and certainly one of my favorites-- the crystals visually stand out much more than you can tell from the pictures.
The majority of the examples I have seen have the crystals somewhat jumbled together, or set against dark green malachite matrixes. As a result, the crystals can be hard to properly appreciate. The contrasting background and distinct nature of the crystals and crystal clusters make the clinoatacamite on this piece easier to discern and appreciate.
I purchased a large lot of Lilly Mine material while in Peru, the bulk of the specimens were mainly just druses of quartz over chrysocolla or malachite, though there were a small quantity of these very rare clinoatacamite specimens as well.
This is one of the top clinoatacamites from the lot and an unusual example of the intersection between rarity and a macroscopic mineral that can actually be called aesthetic.
Clinoatacamite is a hydrous copper chloride.