Let Z 1 , Z 2 , ... be i.i.d. random variables with tail behaviour, where r is a regularly varying function at infinity and R is a positive constant. We consider the problem of estimating the exponential tail coefficient R, by methods mainly based on least squares considerations. Using a geometrical reasoning, we introduce a consistent estimator, whose values lay between the least squares estimates proposed by Schultze and Steinebach (1996). We investigate here the weak asymptotic properties of this geometrictype estimator, showing in particular that, under general conditions, its distribution is asymptotically normal. The results are applied to the related problem of estimating the adjustment coefficient in risk theory (Csörgő and Steinebach (1991)) and a simulation study is performed in order to illustrate the finite sample behaviour of this estimator.