This a Wulfentite specimen from Durango Mexico. Wulfenite is a rare secondary mineral made of lead molybdate. It can form either flat tabular crystals or have a pyramid structure. This specimen has the latter. It also has a nice caramel color that really pops against the dark host rock, making this an awesome display piece.
This piece measures approximately 7.8cm x 5.9cm x 2.5cm and comes secured to an acrylic base measuring 3.75cm x 3.75cm