Sphalerite, Snailbeach.

Sphalerite, Snailbeach.

Sphalerite, (Zn, Fe)S, sometimes called "Black jack" or "Blende", is zinc sulphide, and is the main ore of zinc. Pure sphalerite is ZnS, but as it is usually combined with varying amounts of iron, (Fe) the formula is expressed as (Zn, Fe)S.  Sphalerite with very little, or no iron can be colourless, but as in this specimen, the amount of iron has produced a dark golden brown colour. There are no complete crystals, only fractured faces, and here and there, just a glimpse of the deep red colour usually associated with sphalerite, which is a good aid for identification. The white mineral is calcite, and the specimen was collected from Snailbeach mine, Shelve, Shropshire.

Stilbite with Actinolite, Mt.Painter.

Stilbite with Actinolite, Mt.Painter.

The main component of this specimen is stilbite, with some actinolite surrounding it.  Stilbite, which is a serial name, is a zeolite, and actinolite is a very complex amphibole silicate mineral. The specimen was collected by the club co-founder Jim Nicholls on a visit to Mount Painter, in the Flinders range. E.South  Australia, an area of 800 million years old volcanic rock  The stilbite is a bright orange collection of radiating fibrous crystals, and the actinolite is an indistinct dark green deposit with just a few small observable crystals.

Sphalerite, Snailbeach.

Sphalerite, Snailbeach.

Sphalerite,  ( (Zn, Fe)S),  is zinc sulphide. and is also known as "Black jack "  " Zinc blende " or simply " Blende " by miners. It is the chief ore of zinc, and is found in hydrothermal sulphide deposits in thousands of localities throughout the world. This specimen was collected from Snailbeach mine, in the Shelve area of Shropshire where a small area has been spread with spoil for the convenience of collectors. The specimen is a mass of sphalerite with no discernable crystals. The field of view of the inset is 6mm.

Celestine, (Celestite), Erfoud.

Celestine, (Celestite), Erfoud.

Celestine,  SrSO4  is strontium sulphate. Celestine is derived from the Latin word for celestial, meaning heaven, and further from caelum meaning sky, because it is often pale blue in colour. This specimen is from Erfoud in the Sahara desert, eastern  Morocco, and is a geode lined with colourless, translucent, almost clear, bladed crystals.

Fluorite, Alston moor.

Fluorite, Alston moor.

Fluorite,  CaF2 , also called fluorspar  is  calcium fluoride. The specimen is from Smallcleugh mine,  Alston moor, Cumbria, and seems to be the result of at least two episodes of deposition. The first deposit is one of very small, almost colourless cubic crystals, some of which are edged in deep purple ( see inset 12mm view ). The second deposition is not so widespread, and is an indistinct scab like deposit ,which takes on a pale purple hue in places.  Minor sphalerite is also present on the specimen.