Wordwind mentioned Hardy's "Return of the Native". I could remember only
description on the first page of the laborer with his hands turned by constant
hard work into hooks. So I looked at some sites with literary criticism. I could
not quite understand the way the word "hermetic" was used.The dictionary gives
the term "magical" but that doesn't quite fit.

Hardy’s landscapes are hermetic: they show us the visible world
as a portrait of the invisible, the word of inner states of being. Hardy not
only observes, but he recreates the demanding spirit of the place; the essence
of the novel is a vital and indispensable ingredient of all his novels, primarily
a product of creativeimagination. Wessex is a symbolic microcosm like
Faulkner’s Yoknapatawpha or Joseph Conrad’s Sulaco.

perhaps more related to the mystical or the occult...

I like the idea of transforming. Magical or occult did not seem to fit what he was doing.

Hermetic was a term much bandied about by late 19th and early 20th century occultists. They claimed that there was a magical tradition going back to Hermes Trismegistos (thrice greatest Hermes), the Greek name for the Egyptian god Thoth, which had been carefully preserved in secret to keep it from profane use and persecution by the church. The idea was that magical rites performed in the physical world symbolised the the real magic which was occurring within the magician's soul. There was a very complicated system of symbolisms involved, which are still used in things like lucky colours or stones for different astrological signs. So what your author is trying to say, I think, is that the physical descriptions in Hardy's novels are symbolic of the characters' mental and spiritual states.

Bingley

Bingley--a deep bow of respect, sir. And, thank you.

Dear Bingley, What she said.

Previously, the only way I used "hermetic" was "hermetically sealed" meaning airtight. I'm not sure I'm going to be able to find a way to use Bingley's fine explication, but perhaps I may encounter the word again, and won't be so puzzled.

Speaking of novels and Hermeticism, try Umberto Eco's Foucault's Pendulum. Like everything he has written, a joy for word lovers.

Alchemy was part of the hermetic tradition, and the claim is that the transformation of base metals into gold was symbolic of transforming and refining the alchemist's soul. One of the results of their experiments, apparently, was hermetic sealing, hence the name.

One tool for achieving this transformation was that well known example of the transatlantic divide, the philosopher's stone.

Bingley