THE MINERAL MOCTEZUMITE

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

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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.