Because it is acicular Brochantite largely covered by small crystals of almost transparent gypsum or selenite as mentoned in the caption. In some respects, it is similar to the rosasites or the aurichalcites covered by small calcite crystals from the Ojuela Mine. John S.
You are correct. Because no photo or no photo number was explicitly included in your message, I assumed you were refering to the Brochantite I uploaded at about the same time. I do not like these implicit references to a photo since they can cause misunderstandings as in this case. Explicit refences are much better. Anyway, I corrected the title. Thanks for pointing it out. John S.