This highly aesthetic specimen of MARIPOSA (BUTTERFLY) CALCITE comes from Mina Buena Tierra, in Santa Eulalia, Chihuahua, Mexico. On specimens from this mine, the red phantoms present in two ways: some are completely encased inside larger see-through crystals, while on others the calcite has only grown part way up the phantom, leaving the tip exposed. The protruding phantoms have a dark red layer of hematite, while the crystals that are completely covered were protected from this coating. The calcite crystals can be over 2", and take the "dogtooth" (scalenohedral) crystal habit. I purchased this superb specimen from a Mexican wholesale dealer who was set up in one of the small out-of-the-way mineral shows at the Tucson Gem, Rock and Mineral Show.
The specimens I picked out are the last that will come from this classic locality. The 16th level where the calcite was found, is now underwater, and there are no plans to pump it dry again. It used to be that you had your choice of a hundred banana boxes chock full of these fine specimens, but, sadly, those days are over. I was lucky to find about a dozen good specimens, including some very large ones. After this, there won't be any more.
Then there's the question of the name. So why is it called mariposa calcite? There's a great thread on the mindat.com forum about this topic. To summarize the discussion, it appears that the original "Mariposa Calcite" got its name from the location, a specific Mariposa Mine, and achieved special fame for its fluorescence/phosphorescence, not for the colorful aspect under normal light. (I haven't seen any specimens from Mina Buena Tierra like this). Some specimens that go by this name have "butterfly twin" crystals on them, which look very much like a quartz Japan-law twin with 2 widely outstretched "wings". (Again, I haven't seen any specimens from Mina Buena Tierra with this habit.) Another explanation is that the vivid oranges and reds of this phantom calcite look like the bright butterfly wings, but this is a stretch. Some say its all a marketing ploy, and they may be right. Regardless, today almost any mineral collector will know what you mean when you refer to mariposa calcite, so I guess the name has become a generic term, like Kleenex (i.e., facial tissue).
Mariposa (butterfly) calcite has been popular with collectors for years, coming out in quantity from the Mina Buena Tierra in Santa Eulalia, Mexico, which closed in 2011. This is a fairly large and relatively damage-free example of this material, featuring orange-tipped dogtooth crystals with with sharp, dark red phantoms inside.
8.3" large cabinet size
Prominent dark red phantoms
Sharp dogtooth calcite crystals
Attractive orange-tipped, clear crystals
8.3" x 8.0" x 2.4"
Large 3.4" Peg Stand