The Bausch & Lomb StereoZoom 5 is a stereo zoom microscope produced by the American optical manufacturer Bausch & Lomb, offering a continuous magnification range of approximately 0.7× to 3× at the objective head — expandable with auxiliary lenses — and widely adopted in lapidary workshops, jewellery benches, and gemmological laboratories from the 1970s onward. Its combination of generous working distance, wide field of view, and mechanically robust construction made it one of the most enduring inspection instruments in the trade, and many examples manufactured decades ago remain in active service today.

Design and Optical Characteristics

The StereoZoom 5 belongs to the Greenough-type stereo microscope family, in which two separate optical paths converge at a slight angle to produce genuine three-dimensional perception of the subject. This stereoscopic view is particularly valuable when examining faceted gemstones, as it allows the observer to judge depth relationships between inclusions, evaluate the geometry of facet junctions, and assess surface polish without the ambiguity of a single-axis monocular instrument.

The zoom mechanism operates smoothly through its range without requiring discrete click-stop changes, permitting the examiner to scan a stone at low power to locate features of interest and then increase magnification continuously to study them in detail. The working distance — the clear space between the front of the objective and the specimen — is sufficiently large to accommodate ring shanks, brooch mounts, and other three-dimensional jewellery items beneath the lens, a practical advantage over higher-power compound microscopes whose short working distances restrict the size of objects that can be examined.

Standard eyepieces supplied with the instrument are typically 10× wide-field oculars; substituting 15× or 20× eyepieces extends the upper magnification range, though at some cost to field of view and eye relief. Auxiliary 0.5× and 2× objective lenses can be threaded onto the objective to shift the entire zoom range downward or upward respectively, giving the instrument considerable versatility across different inspection tasks.

Applications in Gemmology and Lapidary Work

For the gemcutter, the StereoZoom 5 serves several distinct functions. During pre-forming, low-power examination reveals the orientation of inclusions, cleavage planes, and colour zones that influence how a rough stone should be oriented before cutting. During and after faceting, higher magnification allows the cutter to assess whether facet edges meet cleanly at junctions, whether the culet is centred, and whether the polished surfaces carry residual scratches or orange-peel texture from an insufficiently fine polishing medium.

For the jeweller and quality-control inspector, the instrument is equally useful: prong tips, bezel edges, and pavé settings can be examined for sharp burrs or incomplete closure, and stones already set in mounts can be checked for chips or abrasion without removal from the piece.

In a gemmological context the StereoZoom 5 is not a substitute for a dedicated darkfield gemological microscope equipped with a rotating polariser, fibre-optic illuminator, and immersion cell — instruments optimised for inclusion identification and treatment detection. It is, however, a capable complement to such equipment, particularly for rapid triage, surface examination, and any task where the large working distance and three-dimensional view are advantageous.

Illumination

Original configurations were supplied with incandescent transmitted and reflected illumination bases. Many units in current use have been retrofitted with LED light sources, which offer cooler operating temperatures, longer service life, and more consistent colour temperature. Fibre-optic ring lights and gooseneck illuminators are also commonly paired with the instrument to provide oblique or directed lighting that enhances surface relief and reveals polish defects not visible under diffuse illumination.

Longevity and the Secondary Market

The StereoZoom 5's reputation for mechanical durability has sustained a healthy secondary market. The zoom body, trinocular heads, and focusing racks were manufactured to tolerances that have proven resistant to the wear experienced in busy workshop environments. Replacement parts, including zoom bodies, eyepiece tubes, and focusing mechanisms, circulated widely enough that competent technicians can maintain and recalibrate used instruments. As a result, a well-maintained example purchased second-hand frequently performs comparably to its original specification, making the model accessible to small studios and independent cutters who require reliable optical quality without the capital outlay of current production instruments.

Bausch & Lomb's scientific instrument division was eventually acquired and the StereoZoom line discontinued as a current product, but the installed base remains large enough that the name is still used as a point of reference when lapidaries and jewellers discuss workshop microscopes.