I am a country with a history deeply intertwined with Berber culture, and I have a diverse landscape ranging from desert to mountains. My economy has been bolstered by phosphate mining and agriculture, and I've experienced periods of significant political change. I am also known for a specific type of date that is quite popular internationally, and my medina is a UNESCO World Heritage site. Which North African country am I?

1. My official languages are Arabic and Berber.
2. My capital is known for its old city and traditional markets.
3. I have a significant coastline on the Mediterranean Sea.
4. My phosphate reserves are among the largest in the world.