Their beauty has already marvelled staff at Cornish attraction Caerhays Castle. Now, an American audience has been taken under the spell of this fine collection of minerals.

The assortment, which is usually kept at the Cornish property near St Austell, are said to be "the envy of collectors worldwide" after becoming one of the star attractions at the Tucson Gem and Mineral Show in the US.

The collection had lain uncatalogued and largely hidden for over 100 years, until it was rediscovered. Some of the specimens have since been transported across the Atlantic to form a stunning display which created a buzz of excitement at the show.

Courtenay Smale, the curator of the Williams Caerhays Mineral Collection, took 24 specimens representing the rare arsenates and phosphates from Cornwall. Also included in the display were a number of important foreign pieces, such as opal from Australia, aquamarine and topaz from Siberia, and silver from Norway.

It was not until Mr Smale began investigations into the minerals that the full extent of the collection was realised.

He said: "There were some minerals in the glass cabinets but so much more not on display.

"I found a cache of minerals in cupboards, then a horde in the cellar.

"On the mantelpiece in the smoking room were topazes and aquamarines from Russia and new discoveries kept on happening – minerals in a chest of drawers in the old vegetable room and yet more in the old cold store."

The Caerhays mineral cabinet at the Tucson event was one of just four special exhibits from outside the United States, and the only one from the UK.

Mineral aficionados from around the world were impressed with the quality of the specimens, with one leading mineralogists saying "it was the finest display in the show".

Within hours of the show's closure, images of some of the Caerhays minerals appeared on the world's most important mineral web sites. The collection now forms part of the Caerhays Castle tour.