Quartz, Herkimer diamond ( type ), Marine colliery.

Quartz, Herkimer diamond ( type ), Marine colliery.

Herkimer diamonds are small doubly terminated quartz crystals. SiO2 and are so named because of their abundance in Herkimer county, New York, USA. This specimen comes from Marine colliery, Ebbw Vale, South Wales, and is exactly the same as those from the USA, but can only be referred to as a Herkimer diamond ( type ) The crystal is exactly one cm. long and is perched on the edge of a vhug of siderite in a brecciated ironstone. From Marine colliery waste heaps, in the clay ironstone beds in the upper Carboniferous coal beds of South Wales.

Siderite, Marine colliery.

Siderite, Marine colliery.

Siderite is Iron carbonate FeCO3  This specimen was collected from Marine colliery waste heaps in Ebbw Vale many years ago. The waste heaps and all sign of the colliery have long disappeared. The clay ironstone bands in the south Wales coal field which are the origin of the specimen, date from the upper Carboniferous period. The specimen is brecciated ironstone with numerous vhugs which are filled with small golden brown platey crystals of siderite.  

Siderite, Marine colliery.

Siderite, Marine colliery.

Siderite is an iron carbonate.  FeCO3   This specimen was collected from a waste heap on the site of the closed Marine colliery in Ebbw vale, south Wales.  Even the waste heap has now been obliterated by developement. The origin is from the upper Carboniferous clay-ironstone beds in the south Wales coalfield. The thin, platy, golden brown crystals line a vhug in ironstone. Other similar specimens from this site will be added later, including some with millerite, and one spectacular Herkimer diamond.  

Pyrite, Unknown origin.

Pyrite, Unknown origin.

Pyrite, FeS2  an iron sulphide, is the most common sulphide mineral. It's distribution is widespread, and it is found in all types of rock. It is also a very common component of hydrothermal mineral deposits. The origin of this specimen is unknown, but it is worth keeping as a type specimen. It is about 75% massive, with an aggregate of small. often intergrown cubic crystals in the remaining 25%

Jet ( Whitby Jet ).

Jet ( Whitby Jet ).

Jet is not a mineral. It does not have a crystalline structure, and is a mineraloid. There are many other mineraloids, amber, opal, and pearl, being just three of the better known ones. Whitby jet is a type locality, and is a " hard jet " that was formed during the early Jurassic period by carbon compression of fossil wood in a brackish salt water environment. An article on "Fossil Wood" can be found in issue 1 of the Silurian magazine, which is also on this website.