In an electric blender, blend the frozen pineapple, pineapple juice, tequila, lime juice, and salt until smooth with no visible pineapple chunks.

Run a lime wedge around the rim of the glasses and invert upside down on a shallow bowl/saucer filled with coarse salt. Twist the glass and move it around, making sure salt flakes are sticking to the rim.

Pour margarita mix into glasses, dividing equally.

Garnish with a slice of lime.