Year-long celebrations to mark two special milestones at Castleton's Treak Cliff Cavern in the Peak District are sure to be sweet thanks to Treacle the truffle hound and an award-winning local chocolatier.

For larger-than-life Treacle - alias cavern owner Vicky Turner in costume - will help visitors sniff out tasty truffles created by artisan chocolate maker Cocoadance on three underground hunts organised to highlight the Derbyshire cavern's 300th anniversary as a Blue John mine and 75th anniversary as a show cave.

As well as making the Blue John-inspired truffles, David Golubows and Bridget Joyce of Cocoadance - based at Mam Farm, overlooking Castleton and the Hope Valley - will also craft a special 75th anniversary chocolate egg to add extra spice to this year's Easter Egg hunts. Everyone taking part will be able to enter a free prize draw to win the scrumptious souvenir of Treak Cliff's landmark year.

Hot on the heels of the first Treak Cliff Truffle Hunt on Saturday March 27 will be a party and cake cutting ceremony on Thursday April 1, the 75th anniversary of the opening of Treak Cliff Cavern as a show cave. Caterer Diane Ridley of The Speciality Sandwich Company of Chesterfield will make the cake and invited guests will share it to celebrate the cavern's birthday.

Throughout 2010, a series of family-oriented and heritage inspired events - including guided Blue John Mining Tours giving an insight into past and present mining techniques - will offer visitors the opportunity to enjoy the festivities.

"It's a very special year for us, and we want everyone to join in the fun," explained Vicky, whose family, the Harrisons, have been involved in running Treak Cliff Cavern for 65 years. "Four generations of my family have worked here since 1945, including my grandparents Harold and Edith, my dad Peter, who's now 83, me and my children John and Lizzie, so over the years it's played a huge part in all our lives.

"We believe Blue John mining started here in about 1709, give or take a year or two, and Treak Cliff opened as a show cave in 1935, so we decided to celebrate both milestones with a series of special events for people of all ages to enjoy."

Added David Golubows of Cocoadance: "It's a great pleasure to be helping Vicky and her team mark Treak Cliff Cavern's milestone year, and Bridget and I welcome the challenge of creating themed truffles and an anniversary egg to make the celebrations even more memorable."

Treak Cliff Truffle Hunts will be held on Saturdays March 27, May 15 and September 25, while Blue John Mining Tours will take place on Sundays March 28, May 16 and September 26. Families can join in a series of Polish Your Own Blue John Stone sessions or celebrate their own special birthdays underground throughout the year, and there will be Carols by Candlelight on the three pre-Christmas weekends in December. Vicky is also collating old photographs of Treak Cliff dating from around 1900 to the present day, which will go on display at the cavern throughout the year.

Castleton is the only place in the world where the unique Blue John stone is found, among the rocks of Treak Cliff Hill and in only two caverns - Treak Cliff Cavern - which features 'The Pillar', the largest piece ever dsicovered, and Blue John Cavern. As a Site of Special Scientific Interest (SSSI) for many years, Treak Cliff Cavern is world famous and geologically important. By agreement with Natural England, all Blue John stone deposits on the visitor route are preserved. Around half a tonne is extracted each year from areas not seen by visitors and made into jewellery, small bowls, ornaments and other decorative items.