Castelmagno is made from pasteurized cow's milk, rarely with the addition of small amounts of a mixture of goat's and sheep's milk. The percentage of goat's and sheep's milk may not exceed 20%, though.
The cheese ages in natural caves for at least one month and up to 5 months (or in some cases more).
Sometimes, Castelmagno is also referred to as a blue veined cheese, but actually, the blue veins may or may not be present in this type of cheese. Unlike Gorgonzola cheese, Castelmagno is not inoculated with penicillium spores. The eventual formation of molds in this type of cheese is due to a completely natural process.
Usually, molds only appear in those forms of cheese aged for more than 5 months. The longer it matures the more blue veins the cheese will develop.