The Constitution of 1988 promotes cooperatives as privileged forms of organizing for the diggers. This paper analyses how diamond diggers from a district of Minas Gerais utilize the cooperative form, having as presupposition that there is an inherent conflict between the cooperative form and the organization of digging activities. This is a case study, for which documents were analyzed and also some of the board members of the cooperative, diamonds diggers members of the coop, local authorities and other relevant informants were interviewed. In this research Contingency Theory and New Institutional Economy are used to explain the genesis of the organization. It is concluded that cooperative organization should not be proposed as a solution for any type of activity. One should take into account the kind of activity and the organizational culture already established by the organization, this time in diamonds digging, which led to an inadequate appropriation, although involuntarily, of a cooperative organizational form.