Cartier, Paris

Bloodstone, a distinctive variety of heliotrope, is a dark green chalcedony known for its vivid red inclusions, caused by iron oxide deposits. Prized since antiquity for both its striking contrast and symbolic significance, it was carved into intaglios and signets by the Greeks and Romans, while in the Middle Ages, it became known as “The Martyr’s Stone,” with legends attributing its red markings to the blood of Christ. Its deep green body, punctuated by crimson flecks, lends it a rich, organic beauty, making it a highly desirable material for decorative objects and fine jewellery.

As seen in the prism clock here, bloodstone’s ability to complement precious metals such as silver and gold makes it an ideal choice for elegant, architectural designs. Here, the bloodstone provides a rich, bold backdrop, dramatically contrasting with the broad polished silver mounts at the front and back of the clock. These mounts were designed not only to create a striking counterpoint to the dark bloodstone but also to draw the eye toward the dial, guiding attention to the mesmerising effect of the prisms as they reveal and obscure the dial in turn. When polished, the stone’s smooth surface enhances the dramatic interplay of green and red, further emphasising its distinctive character. Naturally tarnished with age and storage, the mounts, if polished, would further amplify this interplay between reflection and shadow, heightening the sense of depth and illusion inherent in the design.

Creating a wonderfully playful and innovative optical illusion, the prism clock works on the principles of a periscope. Employing two prisms to reflect and refract light, the timepiece’s dial and hands are made to appear or disappear depending on the viewing angle. A natural complement to Cartier’s famous Mystery clocks, this shared emphasis on illusion and refined craftsmanship demonstrates the cutting-edge innovation that defines Cartier’s horological artistry. Here, technical mastery meets creative elegance, producing a timepiece that captivates the viewer by challenging their eye’s expected perception.

Invented by Gaston Cusin, the patent for the prism clock was delivered on 4 January 1937. Born in 1897, Cusin was a talented and inventive watchmaker who made his first clock at the age of 14. He was an excellent addition to Maurice Coüet’s workshop, joining when the Cartier-affiliated atelier relocated to Paris’s rue Lafayette in 1919.¹

Cartier’s first miniature version of the prism clock dates to 1952 and was owned by Ali Aga Khan, the husband of Rita Hayworth. It is illustrated in F. Chaille & F. Cologni, The Cartier Collection: Timepieces, Paris: Flammarion, 2006, p. 353. With the majority of examples executed solely in silver and/or gold, the distinctive architectural shape and use of bloodstone in the case of the prism clock shown here make it an exceptionally rare and unusual example of the genre.

¹ Hans Nadelhoffer, Cartier - Jewelers Extraordinary, London: Thames & Hudson, 1984, p. 249.