A Greenway lap is a composite polishing lap manufactured originally by Crystalite Corporation and subsequently by Diamond Pacific, consisting of a polyurethane matrix impregnated with fine abrasive particles. Designed for use with water as a lubricant, it occupies a well-established niche in amateur and hobbyist lapidary practice, particularly for polishing cabochons and, to a lesser extent, faceted stones in softer gem materials.

Construction and Materials

The lap's working surface is a cast or moulded polyurethane compound into which abrasive is uniformly distributed during manufacture. Polyurethane is chosen for its moderate hardness, slight resilience, and resistance to water absorption — properties that allow the surface to conform fractionally to a stone's curvature without undercutting edges, a common fault with harder lap materials. The abrasive loading is typically fine enough to produce a pre-polish or final polish rather than a cutting action, distinguishing the Greenway lap from coarser resin-bond or metal-bond grinding discs in the same lapidary sequence.

When the working surface becomes depleted or glazed, it can be recharged with Greenway polish compound — a proprietary slurry or paste supplied by the same manufacturer — restoring cutting efficiency without replacing the lap body. This rechargeability is one of the product's practical attractions for hobbyists working on a modest budget.

Suitable Materials

Greenway laps perform most reliably on gem materials in the lower-to-middle hardness range. Quartz varieties (Mohs 7), feldspar (Mohs 6–6.5), calcite (Mohs 3), and similar minerals respond well to the combination of polyurethane matrix and water lubrication. Harder materials — corundum (Mohs 9), chrysoberyl (Mohs 8.5), spinel (Mohs 8) — are generally beyond the effective range of this lap type; professional cutting of such stones calls for diamond-charged ceramic, tin, or copper laps with oxide polishes such as aluminium oxide or chromium oxide.

Place in the Lapidary Sequence

In a standard cabochon-cutting sequence, the Greenway lap is introduced after grinding and sanding stages have brought the stone's surface to a fine scratch pattern, typically following 600- or 1200-grit sanding. The lap then removes residual fine scratches and brings the surface to a reflective polish. Because the polyurethane matrix is relatively forgiving, it is often recommended in introductory lapidary courses as a first polishing lap, reducing the risk of the overheating or undercutting that can occur with harder surfaces when technique is still developing.

Professional Context

In commercial and professional cutting shops, Greenway laps are uncommon. Professional cutters working with corundum, beryl, or chrysoberyl typically rely on ceramic or tin laps charged with diamond powder or oxide compounds, which offer greater consistency, faster polishing action on hard materials, and longer service life under continuous use. The Greenway lap's slower wear rate and modest cost make it appropriate for the volumes and material ranges typical of the hobbyist, rather than the throughput demands of a production workshop.

Maintenance and Care

To maintain performance, the lap surface should be kept free of contamination from coarser abrasives used in earlier stages of the cutting sequence — cross-contamination is a frequent cause of scratching during the polishing stage. The lap should be rinsed thoroughly between sessions, stored flat to prevent warping of the polyurethane body, and recharged with Greenway polish compound as soon as polishing action diminishes noticeably.