Princess Charlene was spotted wearing her rarely-seen engagement ring amid rumours surrounding her marriage to Prince Albert. Prince Albert II of Monaco, 66, and Princess Charlene of Monaco, 46, attended the Sainte Devote Rugby Tournament at Stade Louis II over the weekend. Charlene donned her stunning ring for the occasion, which includes a massive three-carat, pear-cut diamond flanked by smaller diamonds in triangular arrangements. The princess rarely wears the accessory for an unknown reason, often photographed bare-fingered at official royal events. The ring was crafted by Parisian jewelle…