Siderite is a very common mineral, in lustrous or iridescent deep brown forms, rarely in paler brown translucent balls. Generally it is in sheaf-like bundles, occasionally in ‘bow-ties’. It does occur in rhombs, often with curved multiple surfaces, and these are frequently hollow, with maybe a chabazite or two inside. Possibly the rhombs were originally calcite, coated with siderite, and the calcite has etched out.
Apatite occurs as fine needles, often coated with brown chlorite.
Below: Siderite, chabazite-Na, apatite and chlorite, Bickers Quarry (Simpkins Quarry), Tokatoka, Kaipara District, Northland Region, North Island, New Zealand. Width of view 3mm.
