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Goethite


Mineral: Goethite, Dolomite
Chemistry: FeO(OH)
Size: 125 mm
Owner: Malcolm Southwood
Photographer: Malcolm Southwood

A heavy aggregate of stalactitic goethite, each "stalactite" is concentrically zoned and, where the "stalactites" intersect the display surface, they present a reniform habit.  These reniform surfaces are peppered with pinkish-tan, saddle-shaped rhombs of dolomite (to 1.5 mm).  A small (12 mm) vug on the back of the specimen is lined with sub-mm crystals of white dolomite, with some of the crystals noticeably zoned (when viewed under magnification).