Vanadinite
The apatite-supergroup vanadate that turns up red-orange on Moroccan barite. Heavy, soft, and easy to buy badly.
Vanadinite is lead chlorovanadate, Pb5(VO4)3Cl, hardness 3, forming red-orange hexagonal prisms and tablets in the oxidised zone of lead ore bodies. Andrés Manuel del Río found it at Zimapán, Hidalgo in 1801 and it was named in 1838. Most specimens on the market come from Mibladen and Aouli in Morocco.
In short
- Vanadinite is Pb5(VO4)3Cl, hardness about 3, specific gravity 6.8–7.1 — conspicuously heavy for its size, because of the lead.
- It belongs to the apatite supergroup and forms a series with mimetite and pyromorphite. Colour is a guide to which one you have, not a proof.
- Mibladen and Aouli, in Morocco's Upper Moulouya lead field, supply the great majority of the material collectors see — on white barite blades or brown goethite.
- Arizona defined the species before Morocco did: the Old Yuma and Apache mines, in smaller, darker, sharper crystals.
- It is a soft lead mineral. No dust, no acid, no ultrasonic cleaner, and its own box.
| Species | Formula | Typical colour | Hardness |
|---|---|---|---|
| Vanadinite | Pb5(VO4)3Cl | Red to red-orange | 3 |
| Mimetite | Pb5(AsO4)3Cl | Yellow, orange, brown | 3.5–4 |
| Pyromorphite | Pb5(PO4)3Cl | Green, yellow-green, brown | 3.5–4 |
| Endlichite | Arsenian vanadinite — a variety, not a species | Olive to brown-red | about 3 |
| Crocoite | PbCrO4 | Orange-red adamantine prisms | 2.5–3 |
| Wulfenite | PbMoO4 | Orange to red, tabular | 3 |
| Descloizite | PbZn(VO4)(OH) | Brown to near-black | 3–3.5 |
What vanadinite is, and where it can form
Vanadinite is lead chlorovanadate and a member of the apatite supergroup — structurally the same architecture as apatite, with lead in place of calcium and vanadate in place of phosphate. It sits in a solid-solution series with pyromorphite (the phosphate end) and mimetite (the arsenate end), and intermediate compositions are common. That is worth knowing before you pay a premium for a name: without analysis, the label is an inference from colour.
It is strictly a secondary mineral. Three things have to coincide: a lead orebody, oxidising conditions near surface, and a source of vanadium — usually vanadium leached out of the surrounding sedimentary or volcanic rock and carried in. That combination is uncommon, which is why vanadinite localities cluster in a few arid districts rather than turning up at every lead mine.
Specific gravity runs 6.8 to 7.1. For something that looks like a bright crust on a rock, the heft in the hand is the first honest signal that you are holding a lead mineral.
Mibladen and Aouli: the Moroccan standard
The Upper Moulouya lead field near Midelt has supplied most of the vanadinite in circulation for decades. Mibladen material is the benchmark: brilliant red-orange hexagonal tablets and short prisms, most of them 3 to 10 mm across, on white barite blades or brown goethite. Aouli, in the same field, tends to give crystals on a darker, more ferruginous matrix.
Because it is dug artisanally and specifically for specimens, the quality range is enormous — wider than for almost any other classic species. Crusts of small, dull, crowded crystals are abundant. Sharp, undamaged, well-spaced crystals with full colour saturation on a clean contrasting matrix are not, and the entire difference between a filler piece and a good one lives in those adjectives.
Two specific checks. Moroccan plates are among the most commonly assembled specimens in the trade — loose crystals glued onto a matrix they never grew on — so look at where each crystal meets the barite for adhesive, for a gap, or for a crystal sitting at an angle nothing else on the plate shares. Then look for repairs: a reattached crystal usually shows as a seam or an abrupt change in lustre under a lens.
Arizona, and the other sources
Before Morocco, Arizona defined the species for collectors. The Old Yuma mine near Tucson and the Apache mine at Globe produced deep red hexagonal prisms and hoppered crystals, and the J. C. Holmes claim near Patagonia produced small but exceptionally sharp material. Arizona vanadinite is generally smaller and darker than Moroccan, and a piece with a genuine old Arizona label carries a premium that the specimen alone would not command.
Vanadinite is also recorded from Tsumeb in Namibia, from Touissit in Morocco and from Sierra County in New Mexico, among a scatter of other arid lead districts. Zimapán in Hidalgo, where del Río found his "brown lead" in 1801, is the type locality but has never been a source of collection specimens.
Endlichite, and the arsenic end of the series
Endlichite is the old varietal name for vanadinite in which arsenic has substituted substantially for vanadium, running toward mimetite. It is typically browner, more olive and less fiery than true vanadinite.
It is a variety name, not a species, and separating it from vanadinite by eye is a judgement rather than a determination. If a label offers endlichite as the rarer thing, it is reasonable to ask what it is based on.
Handling: soft, heavy and lead-bearing
At hardness 3 vanadinite scratches against almost anything, and it is the crystal edges and terminations — the part you are paying for — that take the damage. Store plates in their own boxes, on a mount, and never let two specimens touch in a drawer.
It contains lead and vanadium. A solid specimen on a shelf is not a hazard. Dust is: do not saw, grind, sand or dry-brush it, keep it away from food preparation, and wash your hands after handling. The same discipline covers pyromorphite, mimetite, cerussite and every other lead secondary in a collection.
Cleaning is mostly a matter of leaving it alone. Water and a very soft brush at most; acids attack it directly, and an ultrasonic cleaner will shake crystals off the matrix.