Lawren Harris is 'most people's favourite member of the Group of Seven,' says Linda Rodeck of Sotheby's, which is offering his Mountain Sketch XCI (Mountain on the Athabasca River). It is estimated to sell for $400,000-$600,000. (Sotheby's Canada)

An icy and ethereal Lawren Harris mountainscape headlines the Sotheby's Canada auction of Canadian artwork in Toronto tonight.

In Mountain Sketch XCI (Mountain on the Athabasca River), the beloved Group of Seven artist, captured a subject he often depicted: the Rocky Mountains. However, this work also shows signs of his eventual transition toward more abstract forms.

Estimated to sell for between $400,000 and $600,000, the Harris sketch was unearthed from a private collection in Edmonton. The current owner's late father had purchased it from Beth Harris, the artist's wife.

The same collector is also offering works by other Group of Seven artists — A.J. Casson's October – Lake Superior (estimate: $30,000-$50,000) and Arthur Lismer's Twisted Pine, Georgian Bay (estimate: $60,000-$80,000) — who remain a favourite and typically draw high prices at Canadian auctions.

"The growth [of the auction business] in the last 10 years has been unbelievable actually, both internationally and in terms of Canadian art. Ten years ago, you could buy a Tom Thomson or Lawren Harris for $20,000. Now, they go over $2 million for good ones," Sotheby's Canada president David Silcox told CBC News.

German-Canadian artist Fritz Brandtner's Interior (estimate to sell for $15,000-$25,000) is featured on the Sotheby's catalogue cover and has piqued international interest. (Sotheby's Canada)

"Part of it has to do with Canadians being interested in their own painting in a way. Somebody like [the late art collector and publishing giant] Ken Thomson really set a good example, in my opinion, by saying that yes, Canadian art is really important and is really worth paying for."

Along with including familiar names like the Group of Seven and Quebec's Automatistes, the Sotheby's sale will showcase a host of lesser-known and post-war artists slowly gaining more recognition.

"The speed with which collectors come to contemporary art is much slower than it has been in other countries. But the contemporary art area is starting to develop quite strongly," Silcox said.

Highlights of the sale include:

• Barbara Anne Astman's colour print Untitled, From the Red Series (estimate: $25,000-$35,000).
• Fritz Brandtner's painting Interior (estimate: $15,000-$25,000).
• The Jack Bush canvas Glide (estimate: $80,000-$120,000).
• Two Paul-Émile Borduas paintings, Froissement Multicolore (estimate: $350,000 – $500,000) and Bombardement (estimate: $175,000 – $225,000).
• Marcelle Ferron's Sans Titre (estimate: $150,000-$200,000).
• Jean-Paul Riopelle's 1958 work Untitled (estimate $200,000-$300,000).
• Jean-Paul Lemieux's L'Emigré (estimate: $180,000-$220,000).
• David Milne's watercolour Wild Flowers on the Window Ledge I (estimate: $50,000-$70,000).

"The mission that we're on ... is to take our buyers beyond birch trees in the snow," said Linda Rodeck, vice-president of Sotheby's Canada.

The auction is slated for the Royal Ontario Museum on Thursday evening.