Nick, ( Spartans now have to be sure to avoid relegation ! )
Just a bit on the tricky issue of naming pits/collieries
First a bit of background on places....
All parishes in those days were the next level down from "county" They were the forerunners of modern local authorities and comprised of areas of land called "Townships". ( and not necessarily to contain towns)
The two parishes in our area were Horton ( with 5 townships) and Earsdon with eight townships....
Burradon, Seghill, Backworth, Holywell, HARTLEY, South Blyth&Newsham, Seaton Delaval and Earsdon itself.
Within the township of Hartley lay the communities of Hartley Mill, Hartley New Farm, Hartley Harbour ( to be later renamed Seaton Sluice) and Hartley village itself. And several coal pits called Hartley, were contained in this "township", but all abandoned by 1850s.
The open-field site where the Hestor Pit was sunk in 1845 ( to become the "disaster" pit in 1862) lay not in the "township" of Hartley, but within the "township" of Seaton Delaval.
As a community grew up around this new pit, it became known as New Hartley after the name of the company that owned it. This led to folk calling the original Hartley village " Old Hartley" to distinguish between the two.
The early railway station, Hartley or New Hartley station lay in Seaton Delaval township not Hartley township.
Now this bit I am less sure about, seeing you say your grandad worked at the New Hartley (disaster pit-1862 - 404 fatalies ). I believe that after the bodies were removed from underground, the pit was forever abandoned. But later on, 1870s, two NEW pits were sunk, The Hastings and the Melton, just north of the site of the disaster pit.
Pit Name Trivia
*I was born in Bebside Colliery Village, that lay outside the territory of the Township of Bebside, but name after the coal company that owned the pit
* Part of the town of Blyth today is called The Bella or Isabella, which got it's name from a coal pit that was sunk there, which got it's name from a lady within the family of the coal company owner.
* In fields around the area of Low Horton, on the west side of Blyth, in mid 1800s, a coal pit called the Forster Pit, was sunk by the New Delaval Coal Company. Today this area of Blyth is called New Delaval.
Just a few examples of places been named after pits that were sunk there, and not the vice versa, where places gave their names to the pits !
Michael Dixon