By Bill Shelton
Proustite, Pyrargyrite, Pyromorphite, Mimetite & Vanadinite
I can write pages on all five species - for a collector, they all matter since availability is fair or better and all will brighten most any display. According to mindat.org, here are the locality numbers for this group. Proustite – 698 Pyrargyrite – 1,300 Pyromorphite – 1,510 Mimetite – 993 Vanadinite – 605. The first two are the least common and, unfortunately, rather expensive members of this group. For classic localities, one should consider the examples given below. Proustite and pyrargyrite are especially noted from Andreasbrg, Freiburg and Pribram. Also, Bolivia, Chile and Mexico. U.S. localities include Colorado, Idaho, Nevada and New Mexico. Cobalt, Ontario is also important. Pyromorphite, with the most given localities in the group, is noted from Ems, Pribram, Beresovsk, Cumberland and Leadhills. U.S. localities include Phoenixville, PA and Idaho. Mimetite can be found from Tsumeb; Australia is another possible choice. Mexico is famous as well. Vanadinite can be found from Morocco and Africa amongst other worldwide localities. U.S. localities are very common in New Mexico and Arizona. I have found Morocco to be a very prolific source and one could buy as many as one wanted with ease. It may have the fewest localities but it seems to be the most available.
Color is a major concern and I suggest buying the brightest, pure shade you can find. For example, vanadinite from Morocco is often an unpleasant hue with orange and/or brown mixed with red. Get yourself an excellent pure red specimen. They occur on black matrix and, as such, can be very dramatic. The case lighting will affect the appearance so pay attention when selecting case lights for your samples. As some of you know, red is a scantily represented color in the mineral kingdom. The very best proustite can be a vivid red but exposure to light may darken them so keep that in mind. Small crystals with excellent color have been recently available from Morocco but large, excellent crystals are very rare. Chile produced some of the best pieces; these will likely cost a lot!
I do not cover micromounts much in my articles but here we can find affordable representatives of most all the 100 species in this series. You can find modest pyromorphite examples in Massachusetts and Pennsylvania with a little luck even today. In the past, Connecticut produced examples at Canton and Thomaston (pyromorphite) but mostly micro size crystals. A cursory glance suggests some, and perhaps all of these five species can be found in any size range. The last three are likely to be more moderately priced.
A couple years back, I helped prepare and sell about 30 large boxes of mimetite. They were white to clear, mostly small crystals; all were on dark matrix from Mexico. Hundreds of samples were sold; the market seems to have absorbed them all; this is actually a typical circumstance. Samples were highly lustrous and glittered when placed under any type of light. You may already have one in your collection.
Some minerals seem to be stellar examples of misdirection, etc. and, as such, present a collector with perplexing problems; noteworthy might be turquoise. Rarely have I encountered obvious defraudulent specimens within this group under consideration here. I have seen pink fluorite and spessartine samples where additional small crystals were glued onto the matrix to provide a “better:” specimen. None of this has, so far, been seen with these species. In the event a specimen looks too amazing to believe, examine it with care for obvious glued connections. A black light may be useful in this respect. Much has been said regarding fakes and frauds before – you can check on the internet for a detailed report on this topic.
Incidentally, all of the five species are good indicators of possibly valuable ore deposits. Proustite and pyrargyrite are often associated with silver deposits worldwide. Pyromorphite is found with lead and even zinc deposits but it only contains lead. Mimetite, which is noted for lead, also contains arsenic. Finally, as the very name suggests, vanadinite will contain vanadium; it also has lead in its formula. Generally, we would consider vanadinite as a source of vanadium and a minor lead ore.