THE MINERAL MOCTEZUMITE

Chemistry:Pb(UO₂)(TeO₃)₂, Lead Uranyl Tellurite
Class: Sulfates
Subclass: Tellurites
Uses: Only as mineral specimens.
Specimens

Moctezumite is a very rare tellurium mineral discovered in 1965 by Richard Gaines (1917 - 1999), an American minerologist. Its type locality is the Moctezuma Mine, Moctezuma, Sonora, Mexico, hence the name. The Moctezuma Mine is famous for rare telllurium minerals. Other minerals from here include: bambollaite, cliffordite, denningite, emmonsite, spiroffite, tellurium and zemannite. Not only is moctezumite a tellurium mineral, it is also a uranium mineral. The uranium ion in moctezumite is part of a group of ions called the uranyl ion group. The uranyl ion group, UO₂, is unusual in that it is a positively charged (+2) ion group. Most ionic groups, especially those that contain oxygen are negatively charged such as the sulfate ion group, SO₄^-2; carbonate ion group, CO₃^-2; borate ion group, BO₃^-3; phosphate ion group, PO₄^-3; tellurite ion group, TeO₃^-2 and the silicate ion group, SiO₄^-4. Another positively charged ion group is the ammonium ion group, NH₄⁺¹, found in only a few minerals. Remember, moctezumite is a radioactive mineral and should be stored away from minerals that are affected by radioactivity and of course human exposure should be limited.

THE PHYSICAL CHARACTERISTICS:

Color is orange to brownish orange.
Luster is vitreous to adamantine.
Transparency: Crystals are translucent.
Crystal System is monoclinic; 2/m.
Crystal Habits include small granular crystals.
Cleavage is good in one direction.
Hardness is 3.
Specific Gravity is approximately 5.7 (very heavy for translucent minerals).
Streak is pale orange.
Other Characteristics: Specimens are radioactive and index of refraction is very high at 2.11 to 2.12.
Associated Minerals include various other tellurium minerals such bambollaite, cliffordite, denningite, emmonsite, spiroffite, tellurium, zemannite and other tellurates and tellurites.
Notable Occurrences are limited to the type locality of Moctezuma Mine, Moctezuma, Sonora, Mexico.
Best Field Indicators are locality, high density, color, radioactivity and cleavage.