Topaz, and the citrine confusion

Topaz is a fluorine-aluminum silicate that crystallizes independently of quartz, the mineral behind citrine and amethyst. Pure topaz is colorless, and trace elements and natural irradiation in the earth account for the small range of natural colors: pale blue, sherry brown, pink and the prized natural orange-pink to reddish material sometimes called imperial topaz.

At 8 on the Mohs scale it sits comfortably above quartz and most other colored stones, which is why old topaz survives well in daily-wear settings. The one caveat is a single direction of perfect cleavage, meaning the stone can split cleanly along one plane if it takes a sharp knock, in a way a tougher stone like sapphire would not.

Natural, untreated topaz is most often colorless or a pale sherry to pink tone. Natural blue topaz exists but is rare and usually a light, washed-out shade rather than the saturated blues sold commercially today.

The strong sky, Swiss and London blue tones seen in modern and much recent vintage jewelry are produced by irradiating colorless topaz and then heat treating it, a process that has been standard trade practice for decades and produces a permanent, stable color. Natural pink and true imperial topaz command a real premium over treated blue material because they occur without irradiation.

Topaz typically grows with good clarity, and eye-clean stones are common and expected rather than exceptional, which is different from the inclusion-tolerant grading used for emerald or ruby. A cloudy or heavily included topaz is worth noticing rather than accepting.

Beyond irradiation and heat, some topaz is coated with a thin metallic film to produce iridescent colors such as mystic topaz. Coatings are a modern development, they can wear or scratch off at the girdle over years of contact, and they should always be stated plainly rather than left for the buyer to discover.

Topaz is hard enough for daily wear, but its perfect cleavage means a hard, direct knock against a table edge or hard surface can chip or split the stone in a way that would not trouble a sapphire of the same hardness. Set it, and handle it, with that in mind, particularly in a ring worn at the office or in the garden.

We do not recommend ultrasonic or steam cleaning for antique topaz jewelry, since sudden temperature change and vibration are exactly the stress that a cleavage plane responds to badly. Warm water, mild soap and a soft brush are enough for routine cleaning.

Georgian and Victorian jewelers used natural sherry, pink and colorless topaz in closed-back, foiled settings, often alongside seed pearls or as the centerpiece of a simple gold ring, valuing it as an affordable alternative to diamond or a warm complement to yellow gold.

Irradiated blue topaz became widely available from the later twentieth century onward, so a strongly saturated blue topaz in a genuinely antique mount is worth a second look. It may be a later replacement stone, or the piece itself may be more recent than the style suggests.

Citrine, a form of quartz, is the classic look-alike for sherry and honey-colored topaz, and the two were often called by the same trade name in the past. Citrine is softer, at 7 on the Mohs scale, and generally less expensive, so distinguishing the two matters for value even though a jeweler's tools rather than the naked eye are what settle the question reliably.

Pale blue topaz can also be confused with blue quartz or glass at a glance. Weight, the way the stone catches light, and a gemologist's refractive index test are what separate them with confidence.