A matter of grave concern is emerging at the old section of the Warren Cemetery, with white marble headstones and monuments turning a nasty black, reports the Warren Advocate.

The phenomenon seems to be prevalent on the older gravestones dating up to the 1970s, with some so obscured that it is difficult to read the inscriptions. The lettering on some markers also appears to be washing away.

According to website InspectAPedia, black stains on stone are quite often caused by a cyanobacteria Gloeocapsa sp. that not only stain the stone black, but also increase water absorption by penetrating veins in the stone (marble, for example) leading to honeycomb weathering damage to the stonework.

The article states that wet stone exposed to either freeze-thaw cycles or heating by bright sun can be spalled or cracked by these forces.

A Times article reported that originally people believed that the black on stone was due to “weathering”.

The Times continued that only recently have experts begun to realize the important role of both bacteria and fungi in the deterioration of cultural sites around the world.

The article also noted that air pollution can increase the effects of bio-deterioration.

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