This week we started saying our good-byes to this really major painting by Mijili Napanangka Gibson. It's three metres by two metres and it's an extraordinary colour painting. By most people in the industry, it's considered to be her masterpiece.

She was nearly 80 when she painted it and it took her nearly nine months to paint. We've got photographs of her painting it that were taken by her family. You can see all the different layers that she's applied. I love that there's a whole layer on there that's just been over painted and hidden, but it is a part of the painting because it's secret women's business.

The painting itself is an aerial view, a map of Lake Mackay right on the remote Northern Territory, West Australian border. It shows the women's ceremonial grounds. Mitjili was a senior Pintupi woman and custodian of this very important dreaming story.

We've had this painting for nearly five years. It's been one of the few, if not the only painting, we've ever had that's brought people into the gallery purely by word of mouth. People saying, you got to see this painting in Japingka Gallery. We've had people coming in saying, “I've been told I've got to see one special painting, oh there it is.”

It's that sort of painting. It's a major piece and it's a very high price point, but not for what it is. Who knows what it will be worth in years to come. At the moment it's worth just over $100,000 but in years to come, I think there's no limit to it's value. It's an exceptional painting of major importance.

To be honest with you, I'm going to miss it when it's gone. It's been a big part of my daily life for five years. It was sponsored by an American couple from New York who are collectors but not of indigenous art. The husband is the head of a major philanthropic organisation.

People are a little surprised when I mention that it’s going to New York as the apartments there are usually small and this is such a big painting. I guess not all New York apartments are small.

The couple who bought the painting just saw it and fell in love with it. They were here on holiday. I advised them at the time, think about it, don't rush into it. They were going down south for a tour of the Margaret River wine region and to take in the beautiful countryside down there. While they were away, they couldn't stop thinking about it and that's always a good sign that maybe you should consider buying it.

I always advise people to take your time, because whatever you buy you'll probably have for the rest of your life. When they came back, they just had to have it. It's exciting, it's a major purchase and it's probably in effect, their first indigenous art purchase. Most people start at a lower price point, maybe a couple hundred dollars or something. But they just loved it and had to have it. I guess the most interesting element was that they have said to us that once they pass on they want this painting to be to be returned as a bequest to a national public collection in Australia.

Really they're just going to be custodians of the painting before returning it to Australia. It's a lovely story and while I hate to see a painting of this importance and beauty leave the country, it's reassuring to know at the end of the day, it's really just on loan and it will be coming back to Australia one day in the future.