Vanadinite shares the same structure with Apatite and the two share similar crystal shapes at times.
Vanadinite is part of a chemical series with two other minerals;
Pyromorphite (Pb 5 (PO 4 ) 3 Cl) and
Mimetite (Pb 5 (AsO 4 ) 3 Cl).
This series is a little different than most chemical series which involve substitution of cations such as calcium for magnesium.
Instead, this series substitutes its basic chemical units the anion groups; phosphate (PO 4 ), arsenate (AsO 4 ) and vanadate (VO 4 ).
Vanadinite is usually red which the other members of this series and apatite group usually are not.
Vanadinite's classic crystal habit is short hexagonal prisms terminated by a pinacoid, or flat basal face.
These crystals are wider than they are long and are more blade-like than the barrel shaped crystals so common to the Apatite Group minerals.
The high luster and deep red color give vanadinite a nice appeal to mineral collectors.
Color is typically bright red to orange, less commonly gray or brown.
Luster is vitreous to adamantine.
Transparency crystals are transparent to translucent.
Crystal System is hexagonal; 6/m
Crystal Habit is typically the hexagonal prism with pinacoid as a termination.
Rare crystals can have the hexagonal pyramid as a termination.
Can also be found as rounded masses and crusts.
Cleavage is none.
Fracture is conchoidal.
Hardness is 3.
Specific Gravity is approximately 6.6+ (very heavy for translucent minerals)
Considering the small size of the crystals, this is a wonderful vanadinite specimen. They range in size from microscopic to a couple of millimeters, and they rest on a black goethite base which adds contrast to their vivid colors. The vanadinite is a deep orange in some areas, grading to a brown and then to a tan color. Nice!