In a large bowl, sift together flour, baking powder, salt and sugar; mix thoroughly. Cut in butter using 2 forks or a pastry blender. The butter pieces should be coated with flour and resemble crumbs.
In another bowl, mix buttermilk and egg together, and then add to the flour mixture. Mix just to incorporate, do no overwork the dough.
Roll blueberries in flour to coat, this will help prevent the fruit from sinking to the bottom of the scone when baked. Fold the blueberries into batter, being careful not to bruise. Drop large tablespoons of batter on an ungreased cookie sheet.
Bake for 15 to 20 minutes until brown. Cool before applying the orange glaze.
To prepare Orange Glaze: combine butter, sugar, orange zest, and juice over a double boiler. Cook until butter and sugar are melted and mixture has thickened. Remove from heat and beat until smooth and slightly cool. Drizzle or brush on top of scones and let glaze get hazy and hardened.