This is a slab of slate with many specimens of the “tuning fork” graptolites, Didymograptus murchisoni.
Graptolites are very imported index fossils in the zoneation of the British Ordovician.
These are from the Llanvin Series, Abereiddy Bay, Dyfed, South Wales.
This is a thin section of radial growths of Baryte (or Heavy Spar).
This slide shows plumose (literally like feathers) interference structure.
In thin-section it is similar to other sulphates but can be distinguished by its straight extinction, moderately high relief, small 2V and paragenesis.
- Crystals are often intergrown, rosettes, as demonstrated in this TS.
- Four cleavage directions.
- Interference colors rangeup to first-order yellow.
- Sometimes pale colors-brown in PPL with weak pleochroism.
Collected from a mineral vein in the Hope Valley, near Castleton, Derbyshire.
When you next take a stroll along the Pier at Whitby, stop at the light house, and look back towards the town. You will notice that the cliffs on either side of the pier look very different to each other. Why?
THE EAST CLIFFS
The East Cliffs have lots of horizontal layers of dark and light rock—shales and sandstones.
Heliophyllum (or “Horn Coral”) is an extinct Genus of Coral that existed predominantly in the
Devonian (408-360 million years ago).
This well preserved specimen was found in the beechwood limestone (Clark County, Indiana, USA)
This picture of the Heliophyllum horn coral shows the beaded pattern along its septa lines.
Heliophyllum (Rugosa / Horn Coral)