Tapiolite (mineral series that is an ore of niobium and tantalum. The tapiolite group includes tapiolite-(Fe) or ferrotapiolite and tapiolite-(Mn) or manganotapiolite.[ Mindat tapiolite group][ Ferrotapiolite in the Handbook of Mineralogy][ Manganotapiolite in the Handbook of Mineralogy] Tapiolite-(Fe) is by far the more common of the two.[ Tapiolite-Fe on Mindat][ Tapiolite-Mn on Mindat]
The minerals have a submetallic luster and a high specific gravity with tapiolite-Fe having a higher specific gravity (7.90)[ versus 7.72 for tapiolite-Mn.][
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The mineral was named in 1863 after the forest god Tapio of Finnish mythology, and the original tapiolite material came from Sukula, Tammela, Tavastia Proper, Finland.[ webmineral Tapiolite]
Tapiolite is very close to columbite and tantalite. Those minerals have the same chemical composition, but different crystal symmetry orthorhombic for tantalite or columbite and tetragonal for tapiolite.[P. Cerny et al. "The tantalite-tapiolite gap: natural assemblages versus experimental data" Canadian Mineralogist 30 (1992) 587 free download]