What can pearls and whale poo teach us about the nature of life?

Ambergris - aka the "faecal concretion" of sperm whales - is one of the many fascinating natural substances Una Cruickhank investigates in The Chthonic Cycle .

In years past, these stony-looking yet buoyant poo clumps - which can weigh between 15g and 50kg - were in high demand for making perfumes and aphrodisiacs, she says.

"[Ambergris] is extremely valuable, which I think is very, very funny. It's one of the objects that I look at and ask, 'How has this gone from being something quite disgusting to being a luxury object? What are these fascinating human processes that we've put this thing through?"

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Although Victorian-era scientists seemed to be "trying to inhale the entire world" with their rampant collecting, 19th-century Brits were on to something when it came to their strict social rules around death and mourning, Cruickshank thinks.

Mourning jewellery - which made a person's grief "visibly apparent" - was often made from jet, a semi-precious black gemstone produced when the wood of certain trees is exposed to salt water and petroleum.

"I am not at all a person who can live at ease with the idea of death, but over the past couple of hundred years, we have stored it away from everyday life.

"It might be sort of reassuring or good to have a way to communicate visually to people that I'm going through a really bad time right now. Maybe handle me with kid gloves? Have a bit of sympathy?"

Another natural product with an intriguing and chequered history, which Cruickshank explores in The Chthonic Cycle,is pearls.

In 17th-century Venice. it was illegal for anyone - even the very rich - to own Pearls if they weren't a member of the aristocracy, she says.

Contrast that with the genuine pearl necklace bracelet and earring set Cruickshank bought for a "completely insane" $35 while working as a copywriter in the Sydney offices of the discount website Groupon years ago.

"Every single [pearl] represents an oyster that was implanted with a little core to stimulate it. It was raised for months or years, then it was killed. It's bizarre the way that this ended up being a faux luxury for a person - me - who is very, very broke and trying to feel fancy."

Cruickshank has been really moved by the positive response to The Chthonic Cycle, especially after the miserable week of doubt she endured after finishing the book two years ago.

"I definitely remember thinking when I was reading through the final proofs ... 'This is just terrible, like, this is an awful book. This is nonsense written by an idiot who is crazy'."

Although she was recently named one of New Zealand's ten best upcoming authors, growing up, she thought becoming "an acrobat or a rock star or something very glamorous" was her destiny.

"I had this idea as a child that a writer was like an old man who was very dour, which I'm really happy to find is not the case."