Asterism

An optical phenomenon of intersecting lines in a star formation, caused by the reflection of light rays on inclusions . It can be seen in certain cabochon-cut stones such as the star ruby and star...

Brass

An alloy of copper and between 30% and 40% zinc. Can be used to make the plates, bridges and wheels for a watch.

CIBJO

The French acronym for Confédération International pour la Bijouterie, Joaillerie, Orfévrerie translated to The International confederation of Jewellery, Silverware, Diamonds, Pearls and Stones....

Digital

A system controlled by the watch movement to indicate the time. An alphanumerical (or numerical) display uses letters and numerals (or just numerals) to show the time.An...

Etablissage

A procedure for manufacturing the watch and/or movement by assembling the various parts. As a general rule, the procedure in full comprises taking delivery of, inspecting and stocking the...

Flange

The part inside a watch case that supports the movement. dial and the dial plate, freeing space in which many of the striking mechanism parts could be housed. The parts thus placed under...

Gild

To cover an object with a thin layer of gold, generally by electroplating. In a watch, the case but also the movement's plate and bridges can be gilded.

Hematite

A natural iron oxide that is a metallic dark to silver-grey with a high sheen. Hematite can be used to make watch dials. It has a specific gravity of 4.95 to 5.16 and a hardness of 6.5 on the...

Intermediate wheel

A small toothed wheel, part of the hand-setting mechanism.

Jewels

The international term for the jewels (rubies) in a watch movement that are used as bearings for pivots to reduce friction. The movement of a quality watch has between 15 and 21 jewels.

Karrusel

A device similar to the tourbillon, the difference being that the cage is driven by the third wheel. Invented by Bonnicksen, a Danish watchmaker established in London.See complication.

Large date

A date function with large numerals on two independent discs, displayed through oversized apertures. In 1994, A. Lange & Söhne displays for the first the the Large Date in the...

Moss agate

A green variety of agate. It is chalcedony that has dendritic green, red or black inclusions. The inclusions often form beautiful patterns and are used as watch dials or cases.

Natural pearl

A natural pearl is also called an oriental pearl. This pearl is formed by an oyster, freshwater mussel or other mollusc as a reaction to a tiny invading object that happened to be caught inside...

Oscillating pinion

The oscillating pinion, which comprises a mobile stem and two pinions, allows the chronograph to function very efficiently by replacing the two large wheels of the anterior movements. A coupling...

Petite sonnerie

Watch that strikes the hours and quarters in passing without repeating the hours at each quarter. The hour and quarter strikes can be repeated on demand if the subsidiary seconds are...

Quartz

Silicon dioxide. Also called rock crystal. Quartz has the specific property of vibrating at a very high frequency (32 MHz) placed under electric current. Under certain conditions, it...

Sidereal day

A unit of time used by astronomers defined as the interval of time taken by a star to make two successive upper meridian transits.

Terminal coil

The incurved ends of the balance-spring to improve isochronism. Invented by Breguet and perfected by Phillips and others, hence often referred to as a "Phillips curve" or "Breguet overcoil".

Ultra-complicated watch

Any function other than the indication of hours, minutes and seconds, regardless of whether the mechanism is hand-wound or self-winding, mechanical or electronic, and of movement height. The...

Vermeil

Silver covered with a thin layer of gold.

Waterproof

Describes a watch which, in theory, will not let in water at a depth of up to 3 atm or 30 metres.See also ATM; water-resistant.

Year

A four-digit indication of the current year that changes automatically at midnight on December 31st.

Zodiac

At the heart of countless legends and beliefs, since ancient times precious stones have had symbolic value. From the Jews to the Egyptians, each culture and religion has given a different meaning...