Manganese oxide, MnO2, dendritic variety. The specimen was collected from the abandoned Llanymynech limesone quarry about 20 years ago. Sometimes the manganese oxide is wrongly referred to as pyrolusite, but there are several manganese oxides, and only laboratory analysis can determine which of the oxides is present. Dendritic pyrolusite is rare, and more often than not, it is one of the other oxides. Trace elements of other minerals will determine which one.
Haematite nodule, Fe2O3 iron oxide. with siderite and quartz. This specimen was found on my final visit to Marine colliery waste heaps. Hoping to find some millerite, I arrived to find that the waste heaps had been landscaped out of existence. As I was despondently leaving the remaining tiny car park, I spotted this nodule by the entrance, which did at least give me something to show for my 136 mile round trip. The centre of the nodule is lined with tiny platey siderite crystals, with two small crystals of quartz.
Jasper, Mookaite var. SiO2 , is not a mineral as such, but is a rock. It is formed as a sedimentary rock from the weathered products of a Cretaceous siltstone in the Carnarvon basin in Western Australia. In particular it derives it's name from Mooka station, where it was first found. Jasper is an aggregate of microgranular quartz, and chalcedony. The specimens reddish colour is the result of iron impurities, and the typical conchoidal fracture of quartz is apparent. This specimen was collected by Jim Nicholls, co-founder of the club, while he was working in the area.
Hematite, Fe2O3 iron oxide, with siderite, FeCO3 iron carbonate. The haematite in this specimen is in the form of many angular shards, which were created as the result of hydraulic brecciation. The spaces and voids have been populated by small platey crystals of siderite. Also on the specimen is one " herkimer " quartz crystal. The specimen was collected from Marine colliery waste tips, near Ebbw Vale, south Wales
Barite, or Baryte, BaSO4 is barium sulphide. This specimen is peculiar to cliffs on the north coast of the Isle of Sheppey, in Kent. The cliffs, which are in the London clay, are host to large septarian nodules. The nodules have cracks which are lined with pale mustard coloured calcite, on which there are radiating greyish white barite crystals. How this type of mineralisation occurs seems to be a mystery.