THE PYROCHLORE GROUP OF MINERALS

MICROLITE	PYROCHLORE	BETAFITE

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The Pyrochlore Group of minerals includes some unusual, obscure and isometric (4/m bar 3 2/m class) oxides. Several belong to the informal group called the rare earth oxides. The Pyrochlore Group is composed of basically three minerals and members of their respective subgroups. The subgroups are named after pyrochlore, betafite and microlite, the three most common and most well known members of the pyrochlore group.

Members of the group have the general formula A1 - 2B2O6(O, OH, F) - nH2O. The A can be any of a long list of metal ions: lead, calcium, potassium, bismuth, sodium, barium, cerium, cesium, tin, strontium, thorium, uranium, yttrium, zirconium and/or antimony. The B represents a different position in the structure and can be any of these metal ions: iron, niobium, tungsten, tin, tantalum and/or titanium. Typical formula for the three main members of the Pyrochlore Group look like this:

• Betafite (Ca, Na, U)2(Ti, Nb, Ta)2O6(OH, F)
• Microlite (Ca, Na)2Ta2O6(O, OH, F)
• Pyrochlore (Ca, Na)2Nb2O6(OH, F)

Compare the general formula of the very closely related and also isometric Stibiconite Group. Although closely related to the Stibiconite Group, the two groups are dramatically different in their general crystal habits. The Stibiconite Group rarely forms good crystals whereas the Pyrochlore Group is known for fine crystal forms of the isometric system.

• Bariomicrolite (Barium Tantalum Niobium Oxide Hydroxide)
• Bariopyrochlore (Barium Strontium Niobium Titanium Oxide Hydroxide)
• Betafite (Calcium Sodium Uranium Titanium Niobium Tantalum Oxide Hydroxide Fluoride)
• Ceriopyrochlore-(Ce) (Cerium Calcium Yttrium Niobium Tantalum Oxide Hydroxide Fluoride)
• Cesstibtantite (Cesium Sodium Antimony Tantalum Oxide)
• Kalipyrochlore (Hydrated Potassium Strontium Niobium Oxide Hydroxide)
• Microlite (Calcium Sodium Tantalum Oxide Hydroxide Fluoride)
• Natrobistantite (Sodium Cesium Bismuth Niobium Tantalum Antimony Oxide)
• Plumbobetafite (Lead Uranium Calcium Titanium Niobium Oxide Hydroxide Fluoride)
• Plumbomicrolite (Lead Calcium Uranium Tantalum Oxide Hydroxide)
• Plumbopyrochlore (Lead Yttrium Uranium Calcium Niobium Oxide Hydroxide)
• Pyrochlore (Calcium Sodium Niobium Oxide Hydroxide Fluoride)
• Stibiobetafite (Antimony Calcium Titanium Niobium Tantalum Oxide Hydroxide)
• Stibiomicrolite (Antimony Calcium Sodium Tantalum Niobium Oxide)
• Uranmicrolite (Uranium Calcium Cerium Tantalum Niobium Oxide Hydroxide Fluoride)
• Uranpyrochlore (Uranium Calcium Cerium Niobium Tantalum Oxide Hydroxide Fluoride)
• Yttrobetafite-(Y) (Yttrium Uranium Cerium Titanium Niobium Tantalum Oxide Hydroxide)
• Yttropyrochlore-(Y) (Yttrium Calcium Sodium Uranium Niobium Tantalum Titanium Oxide Hydroxide)