THE MINERAL WULFENITE

Chemistry: PbMoO4, Lead Molybdate
Class: Sulfates
Uses: A minor ore of molybdenum and as mineral specimens.
Specimens

Wulfenite is a nice collection type mineral and is popular as such. Its strong colors, nice luster and one-of-a-kind crystal habits attract the attention of many collectors around the world.

Wulfenite is an enigma in terms of its symmetry. There are conflicting results of various symmetry tests and this usually does not happen. It is either a symmetry of 4 or 4/m. The difference is the disputed existence of a mirror plane perpendicular to the four fold axis. If the mirror exists, then the crystals should have a top that is a mirror image of its bottom. Although most crystals don't show it clearly, the bottom pyramidal faces slant at a different angle from the top pyramidal faces. This demonstrates the symmetry of just 4. However, other tests of its symmetry show a 4/m symmetry. This symmetrical oddity only adds to wulfenite's interest among serious collectors.

PHYSICAL CHARACTERISTICS:

Color is red, orange, yellow, silver and white.
Luster is vitreous.
Transparency: Crystals are transparent to translucent.
Crystal System is tetragonal; 4/m or 4
Crystal Habits include very thin square or octahedral pinacoidal plates with pyramidal faces truncating just the edges of the crystal. At times the pyramids become prominant and psuedo-dipyramidal crystal habits are seen, sometimes because of twinning. Prismatic faces are also seen and can make psuedo-cubic crystals. Also encrusting and cavernous aggregates due to intergrowth of crystal plates.
Cleavage is perfect in one direction.
Fracture is conchoidal.
Hardness is 3.
Specific Gravity is approximately 6.8 (very heavy for translucent minerals)
Streak is white.
Associated Minerals are mimetite, limonite, smithsonite, vanadinite and galena.
Other Characteristics: index of refraction is 2.28-2.40 (very high, but typical of lead minerals).
Notable Occurances include Morocco; Tsumeb, Nambia; Mexico and Arizona and New Mexico, USA.
Best Field Indicators are crystal habit, color, density and luster.