But no one is more heartbroken than the owner Aileen Roberts who inherited the crystal from her younger brother James Curtin when he died three years ago.

Mr Curtin found the stone in the local area in 1993, and in 1998 he allowed the gem to go on display at the Wing Hing Long Museum.

The theft occurred at around 1am on Saturday, and officers from the New England Police District were notified later that day.

An emotional Mrs Roberts said she was devastated by the loss of the monster mineral, and not because of its extraordinary financial value.

"It has a lot of sentimental value," she said.

"I hope whoever took it doesn't break it up because it will lose its value and wouldn't be worth anything. James found a few other beautiful things, but nothing like that."

James and Aileen Curtin grew up at Old Mill in a well-established fossicking family. When the quartz rock passed to her, Mrs Roberts was asked if she wished to take the stone from the museum.

"But why would I want to lock it up when it could give people so much pleasure?," she asked Australian Community Media on Monday.

"Everybody loved it, and people came from all over the country to this museum, and some of them came just to look at that stone."

The speed and method of the theft suggest professionals who knew what they were doing, Mrs Roberts said.

But Danny Coleman, the president of the volunteer committee that runs the Wing Hing Long Museum on behalf of Inverell Council, said it was useless to speculate.

The Wing Hing Long and Company Store in Tingha was turned into a museum to raise awareness of the contribution the Chinese made to rural communities in NSW.

During the mining boom peak between 1880 and 1920, a large community of Chinese miners established themselves in the district. This community sought Chinese goods, services and general supplies.

In 1881, the site where Wing Hing Long is situated was purchased by Inverell storekeeper Ah Lin to establish a general store servicing the tin mining communities of the Tingha district.

It remained a working store until 1998, when the Pratt family sold the building (and most of its contents) to Guyra Shire Council for community management by the Tingha Progress Association.

Following council amalgamations and boundary adjustments, the Inverell Shire Council has been the auspicor for this 'living museum' for the past two years.

Mr Coleman agreed the stolen stone was a popular feature of the state heritage-listed museum.

"We've got a lot a lot of interesting things here," he said. "We've got Chinese heritage and mining history, but that rock was a highlight and a lot of people came here and took pictures of it."

From the outside the museum looks as low-tech as its age would suggest , but Mr Coleman said security was good and motion sensors 'are everywhere'.

"I'm getting the security mob to come out today and check everything," he said.

"That's how I was notified. The security company called me, and within minutes I was here because I only live 50 yards away, but they had already gone - so they were well organised.

"But it is going to be very hard to dispose of unless someone just sits it up in their lounge room."

Inverell Shire Council general manager Paul Henry said while the museum contents are insured, and the stone's value was factored into the value of the total contents, it was not listed separately.

"We've advised our insurers of the theft, and we're awaiting their advice on the implications of that," he said.

The fact that the museum was run entirely by volunteers who worked many hours demonstrated its importance to the community.

"This robbery must be a slap in the face for these hard-working volunteers," Mr Henry said.

"It is extremely valuable to us. The benefit the museum brings to not only Tingha but the wider region is not lost on the council."

In the last two years, Inverell Shire Council has invested 'considerable money' in upgrading and preserving this valuable tourism asset, Mr Henry said.

"There's been a new roof put on, there has been lighting upgrades, and there's been a plan prepared for the conservation of the exhibits and how those exhibits are best displayed," he said.

Part of that upgrade was the installation of the motion sensors, which alerted Mr Coleman to the theft within minutes.

"The next item on the improvement plan was to put in security cameras," Mr Henry said.

"But we did have a very high-tech mobile security camera out in Tingha on Saturday, and we are just checking that footage now to assist the police with their investigation."

The stolen item is described as being a 'dark brown smoky quartz grass stone'.

Anyone who may have been in the area or has any information about the theft should contact Crime Stoppers on 1800 333 000.

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