A dark coloured stone, slate is a fairly durable stone commonly used for tiles in roofing, but slate can also be used for paving.
– Slate quarries in Wales used to be massive, whilst production has reduced, it is possible to buy slate from Wales, which will reduce the environmental costs caused from transport.
– Whilst durable, slate is not as durable as most other stones, and heavy rains and frost can chip it. (ref)
– Spain, Brazil and China are all big exporters of slate to the UK. Research has demonstrated that relative emissions for transporting slate from Spain to the UK is around 800kg, with Brazil’s emissions being around 4400kg and China being the highest polluter at 8000kg. (ref)
Slate can be locally sourced, notably from Wales. Local stone will not travel as far to get to gardens and it will not have as big of an impact for the environment and climate, whereas stone imported from further away emits a lot more carbon and can help contribute to enhanced climate change. Another downside to Slate can be seen in its durability, whist fairly durable, heavy rain and frost can chip it, and considering that the UK gets both of these, it may be worth looking at alternates and harden materials such as Bricks or Granite.