I find Wikipedia a great data base giving information which no other encyclopedia would give.
I do my bit when somebody tries to mutilate (not edit) an article by, for instance, deleting whole paragraphs or links just because he/she does not like it.
Mimetite is a leadarsenatechloride mineral (Pb5(AsO4)3Cl) which forms as a secondary mineral in lead deposits, usually by the oxidation of galena and arsenopyrite. The name derives from the Greek Μιμητής (mimetes), meaning "imitator," and refers to mimetite's resemblance to the similar mineral pyromorphite. This focus-stacked photograph shows a 3 cm × 1.7 cm × 1 cm (1.18 in × 0.67 in × 0.39 in) sample of mimetite collected from the Congreso-León mines in the Mexican state of Chihuahua.Photograph credit: Ivar Leidus