The luxury industry's star pupil has aced its latest test, and there are hopeful signs for other brands that have struggled to keep up.

Shares in Cartier's owner Richemont rose 6% this morning after it reported a 20% sales increase for the three months though June. Growth was almost double what stock analysts were expecting.

Richemont has been booming for nearly two years thanks to its large jewelry business. Jewelry is the fastest-growing category in the luxury goods industry at the moment. Sales of Richemont's brands including Cartier, Van Cleef & Arpels and Buccellati rose 24% in the quarter compared with a year ago. The company's jewelry division has grown by more than 10% for seven consecutive quarters and shows no sign of slowing.

But demand also widened to other products. Richemont's specialist-watch division grew 8% in the quarter. Even sales at its fashion and accessories brands, which have been a weak spot, rose almost a 10th.

The hot debate in the luxury industry is whether two years of stagnant sales are a temporary blip, or a sign that brands fundamentally damaged their businesses by hiking prices too aggressively during the pandemic and becoming lazy on innovation. They have been working hard to launch more exciting designs and to introduce new products at lower prices.

Two important data points to watch this luxury earnings season are the rate of growth at LVMH's fashion and leather goods division, and Hermes's handbag sales. Both companies report results the week after next and their performance will be heavily scrutinized.

A recovery in handbag sales is important for the industry because the category boosts profit margins and improves sales productivity at luxury stores.

A strong showing at either company would reinforce early signs at Richemont that appetite for luxury goods is finally widening to products other than jewelry.