Mila Kunis was ''anxious'' about going au naturel for her new Gemfields shoot.

The 30-year-old actress was shot by esteemed fashion photographer Peter Lindbergh for the ethical jewellery company's 2014 campaign, Beauty By Nature, and admits the bare-faced brief made her nervous before she stepped on set.

She told ''When we talked through the direction and that the focus was on natural beauty - which really meant no make-up, no blow day and no retouching - I have to say I was a little anxious. Peter has a way of making you feel bare and raw, but in a funny way it's the most beautiful I have ever felt on a photo shoot.''

Mila jetted off to Zambia to visit the Kagem emerald mine where the precious stones are sourced and was humbled by the experience.

She added: ''The visit to the Kagem emerald mine was fascinating and the trip itself was unforgettable - it was also the first time I'd been to Africa!

''These gems have been forming underground for millions of years, and for me to be the first person to touch them - well you really start to appreciate their rarity.''