Goethite, Ton Mawr.
Goethite is an iron bearing hydroxide mineral. a- FeO ( OH ). This specimen has a vugh of acicular goethite crystals. set into a small piece of haematite. It was collected from Ton Mawr quarry, near Cardiff, South Wales.UK.
Goethite is an iron bearing hydroxide mineral. a- FeO ( OH ). This specimen has a vugh of acicular goethite crystals. set into a small piece of haematite. It was collected from Ton Mawr quarry, near Cardiff, South Wales.UK.
Calcite, calcium carbonate, CaCO3 I discovered this unusual geode in an excavation for industrial buildings in Bridgenorth, Shropshire. The excavation was in sandstone which is predominant in Bridgenorth. The outer shell of the geode is composed of rounded and angular sandstone grains of sizes from .5 mm to 3mm set in a calcite cement. The main core is massive calcite, and the crystals of calcite in the centre are mainly indistinct crystals, but with a few obsevable scalenohedral crystals, nearly all with a brown coating.
Calcite, calcium carbonate, CaCO3 This specimen was collected from Ton Mawr limestone quarry, near Cardiff, South Wales. The fractured surface of the limestone has a distinct purple tint. There are about twenty of white nail-head crystals of calcite resting on a surface covered with minute rust coloured calcite crystals, many of which are rhombohedral.
Opal, common Opal. SiO2 . nH2O. Opal is a hydrated amorphous form of silica, and so it is classed as a mineraloid. This common opal variety is from the Norseman opal mine in Western Australia, and is locally known as gold lace opalite. The variety is described as being a yellow brown opal with black dendritic inclusions. This specimen is as the variety description, and was collected by Jim Nicholls, co-founder of our club while living near Norseman.
Tourmaline is a crystalline boron silicate mineral. There are several varieties and colours. This specimen of dark black elongated crystals will be described as the schorl var. The matrix is feldspar with minor quartz. It was collected from Colcerrow quarry in Cornwall.