Siderite (CWO)

Siderite (CWO)

Siderite, Iron carbonate, FeCO3. This mineral is fairly common throughout the Central Wales orefield. This specimen is from Geufron mine, on the edge of the Hafren forest, near Llanidloes. It is composed of closely packed crystals, with very few that are exposed to view. Those that are, as in the inset picture, have a slight curvature on the crystal faces, which helps to identify the mineral. The Geufron mine waste heaps are a good source for copper secondary minerals.

A Bagley collection introduction.

A Bagley collection introduction.

I have a very large basement area, and this photograph is my store of all things geological, including my collection of rocks, fossils, and minerals. There are many hundreds of specimens, and it will take me a long time to put all of them on the website. Many  minerals  have been collected here in the Central Wales Orefield (CWO). Unfortunately many of the sites have been overgrown, or "landscaped", leaving only a handful of local sites which may still yield the odd specimen.

Calcite, Ton Mawr.

Calcite, Ton Mawr.

Calcite, Calcium carbonate, CaCO3.  This specimen is a fine cluster of creamy nailhead crystals on a limestone matrix. I collected it from Ton Mawr quarry at Pentyrch, near Cardiff.

Calcite.

Calcite.

Calcite, Calcium carbonate, CaCO3  The club had a field trip to the coastal exposures at the small village of Tonfanau, about two miles north of Towyn, We noted a small quarry as we were leaving the village, and decided to investigate. There were several specimens of calcite crystals on the quarry floor, and this is one of them. I later discovered that the crystals were from the walls of calcite pockets in the quarry face. Although the crystals are not perfect, and maybe not very interesting, I was tempted to bring a specimen home.    

Vermiculite.

Vermiculite.

Vermiculite is a hydrous phylosilicate mineral, (Mg,Fe2+, Fe3+ )3(Al,Si)4O10 (OH)2 . 4H2O  This clay mineral has the property of  expansion to 8 to 20 times of its original size when heated, which makes it very useful in cement, and insulation products. It is also widely used as a soil additive in gardening products. This particular specimen is from Ontario, Canada.