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....
Black magnetite octahedra, some with traces of chlorite on their faces, some of which are stepped. Some magnetite crystals are completely encased in chlorite. Blocky orthoclase crystals form part of the cavity lining. Brown sheaf or club-shaped siderite, yellow hexagonal chabazite-Na, and needles of apatite coated with chlorite. Below: Magnetite,...
Gypsum tends to usually occur alone or with barite, chabazite-Na and analcime in the more weathered rock. It forms sprays of clear needles, or larger flat crystals. Below: Gypsum, chabazite-Na, Bickers Quarry (Simpkins Quarry), Tokatoka, Kaipara District, Northland Region, North Island, New Zealand. Width of view 6mm.
Chabazite-Na (“herschelite“) crystals are found in many vugs, as single yellowish, cream, white or colourless hexagonal plates, with striated prism faces and matt-finish flat surfaces. Under magnification the flat surfaces are shown to be made of many tiny points. These crystals are splendid examples of the “herschelite” crystal shape, and...
Chabazite-Na (“herschelite“) crystals are found in many vugs, as single yellowish, cream, white or colourless hexagonal plates, with striated prism faces and matt-finish flat surfaces. Under magnification the flat surfaces are shown to be made of many tiny points. These crystals are splendid examples of the “herschelite” crystal shape, and...
Apatite occurs as fine needles, often coated with brown chlorite. Occasionally it is strung with tiny “herschelite” (chabazite-Na) crystals. Below: Prismatic coated apatite crystal with yellow hexagonal chabazite-Na and orange chlorite. Width of view 6mm.
Analcime is found as small water-clear trapezohedra, occasionally with white cores, and often with square c-faces. Larger crystals are usually crackled and clouded. It is associated with most other minerals, but less common in vugs, and analcime is the mineral most likely to be found coating old fractures. Below: Three...
Bickers Quarry (originally described as Simpkins Quarry) has been owned by Mr. S. Bicker. It is on the north side of Tokatoka Road, a short way east of the junction with Simpkin Road, about 3.5km northeast of Tokatoka (Fig 1 and Fig 2). Tokatoka is about 15km southeast of Dargaville...
Octahedral magnetite crystals with yellowish chabazite and dark brown siderite. Chabazite-Na (“herschelite“) crystals are found in many vugs, as single yellowish, cream, white or colourless hexagonal plates, with striated prism faces and matt-finish flat surfaces. Under magnification the flat surfaces are shown to be made of many tiny points. These...
