A bit confusing?

[Ellie]

On my great grandfathers wedding certificate i'm interested in the occupation of his father and his spouses father. I'm also a little puzzled. One occupation is given as 'miner' and another occupation is given as 'collier'. I thought these were the same?
The certificate is 1901, any ideas why the occpations of my great grandparents fathers are written differently when they appear to be doing the same job? thanks

 

[Edward]

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[Ellie]

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[patrickw]

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[Ellie]

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[benny1982]

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