carboniferous color variation

[nala]

Only Sphenopteris samples,other colors?

[Manticocerasman]

Nice Nala,

The red color on the first one is due to the exothermic reaction of pyrite with oxygen inside the spoil tip.

In other words: those stones are baked due to the heat of the chemical reaction inside the spoil tip (Terril)

This reaction heating up the spoil tip even creates a microclimate or micro biotope around them, resulting in the appearance of plants that normally only appear in southern regions.

[Manticocerasman]

Nice Nala,

The red color on the first one is due to the exothermic reaction of pyrite with oxygen inside the spoil tip.

In other words: those stones are baked due to the heat of the chemical reaction inside the spoil tip (Terril)

This reaction heating up the spoil tip even creates a microclimate or micro biotope around them, resulting in the appearance of plants that normally only appear in southern regions.

a little more detail on Wikipedia:

Subterranean combustion

As some spoil tips resulting from industries such as coal or oil shale production can contain a relatively high proportion of hydrocarbons or even coal dust, they can commence spontaneous subterranean combustion, which can be followed by surface fires. In some coal mining districts, such fires were considered normal and no attempt was made to extinguish them.^[1]

Such fires can follow slow combustion of residual hydrocarbons. Their extinction can require complete encasement, which can prove impossible for technical and financial reasons. Sprinkling is generally ineffective and injecting water under pressure counter-productive, because it carries oxygen, bringing the risk of explosion.

The perceived weak environmental and public health impact of these fires leads generally to waiting for their natural extinction, which can take a number of decades.

[nala]

Thanks Kevin,for your scientific add,i would like to find the brown color