The perfume of the earth — harnessing the natural essence of stone

Supermarket pharmacies often seem to have been squashed into whatever space is available. Some of my regular locum days were spent between the bakery and delicatessen counters. They were days of terrible temptation for a man who needed to lose some weight.

(By the way, a friendly smile and cheerful greeting to passing members of staff often results in a useful tip-off as to when the fresh produce and cooked food is to be reduced in price. A tasty supper for a mere pound or two can be some compensation for those long supermarket shifts.)

Inevitably, during the odd quiet moment, conversation turned to our favourite smells. We discussed the latest perfumes and talked about the smell of new clothes, of newly washed babies, the interior of new cars, the full English (or equivalent) breakfast and leather.

We reminisced about popular perfumes from our teenage years. Do you remember Coty L’Amaint? Flair? Hai Karate? We agreed about the wonderful smell of grandmother’s baking days, of newly cut grass and of rain falling on hot, dry earth.

The smell of rain falling on parched earth or “perfume of the earth” is the rough translation of matti ka attar. This perfume is traditionally manufactured near Lucknow in Uttar Pradesh, northern India, using a simple process whereby discs of clay are left exposed to the hot sun for a couple of months. The discs are broken up before the rains come, distilled in steam and the resulting perfume absorbed in sandalwood oil.

I. J. Bear and G. R. Thomas, of Australia’s national science agency, the Commonwealth Scientific and Industrial Research Organisation, experimented with this technique using various types of stone. They took basalt from an extinct volcano, granite, quarry rubble and the contents of mine spoil heaps, among others, and roasted the material to remove any vegetation or microscopic organisms.

The samples were left out in the Australian sunshine for a few months and then crushed and distilled in steam. Regardless of the type of stone used, the distillate always had the same smell, that of rain falling on hot, dry earth.

A study by the US National Academy of Sciences calculated that the earth’s vegetation releases 438 million tons of volatile oils and essences into the air each year. They believe that over the centuries this has been absorbed by rocks and soil to become the source of this evocative scent, which they called petrichor — the essence of stone.