The Icon of the American Southwest

Turquoise has captivated humanity for millennia, from the burial masks of Egyptian Pharaohs to the iconic silver jewelry of the Navajo and Zuni artisans in the American Southwest. Its striking, opaque sky-blue and sea-green colors, often webbing with dark, contrasting matrix, make it a staple in any lapidary artist's inventory.

However, turquoise is vastly different from cutting agate or jasper. It is extremely soft, highly porous, and prone to crumbling if handled incorrectly. To master turquoise, you must understand the material's physical limitations and significantly adjust your standard lapidary workflow.

1. Understanding the Rough: Natural vs. Stabilized

Before you turn on your lapidary saw, you must know what kind of turquoise you are holding.

Natural Turquoise

High-grade, natural turquoise is quite dense and has a Mohs hardness of around 5 to 6. It can be cut and polished straight out of the ground. However, this high-grade material represents less than 10% of all mined turquoise and is incredibly expensive. The vast majority of natural turquoise pulled from the ground is known as "chalk." It is so soft and porous (hardness 3 to 4) that you can scratch it with your fingernail. If you press chalk turquoise against a diamond wheel, it will instantly crumble into blue mud.

Stabilized Turquoise

To make chalk turquoise usable for jewelry, lapidaries developed the stabilization process. The rough stones are placed in a vacuum chamber and submerged in clear, liquid epoxy resin. The vacuum sucks the air out of the porous stone, pulling the liquid plastic deep into the cellular structure of the rock. Once the epoxy cures, the stone becomes hard, durable, and highly polishable. Note: Stabilized turquoise is entirely real turquoise, just structurally reinforced. This is the industry standard.

Block / Reconstituted Turquoise

Beware of "block" turquoise. This is not rock; it is turquoise dust, dye, and plastic resin pressed into a brick. It cuts like plastic and smells like burning chemicals on the grinding wheel. It holds very little value.

2. Cutting and Preforming Turquoise

Because it is so soft, turquoise cuts extremely fast. You must use a very gentle touch.

The Coolant Rule: No Oil, No Dirty Water

Turquoise is like a sponge. If you use lapidary cutting oil on your trim saw, the oil will soak deep into the stone, permanently staining it a muddy, dark green. Always cut turquoise with fresh, clean water. Furthermore, do not use the dirty, recirculated water from the bottom pan of your cabochon machine. The dark rock dust suspended in the dirty water will soak into the turquoise, turning the beautiful blue color a dingy grey. You must use a fresh-water drip system.

The Preform Stage

When shaping the outline of your cabochon on the 80-grit wheel, be aware that the diamond wheel will chew through the turquoise very quickly. It is very easy to accidentally grind past your template line. Use light pressure and check your progress every few seconds.

Dealing with the Matrix

The dark "matrix" lines running through turquoise (often limonite or pyrite) are usually softer or harder than the turquoise itself. This can cause undercutting, where the matrix grinds away faster than the blue stone, leaving a bumpy surface. To prevent this, use light, sweeping motions on your soft resin wheels to keep the surface perfectly flat.

3. The Polishing Process

Because of its softness (even when stabilized), turquoise rarely requires the aggressive grinding of a 220-grit wheel. Many lapidaries move straight from 80-grit shaping directly to the 280-grit soft resin wheel.

Progress through your soft resin wheels (280, 600, 1200, 3000) using a very light touch. The stone should look perfectly smooth with a soft, satin sheen.

The Final Polish

While cerium oxide works wonders on hard stones like agate, it is generally ineffective on soft stones like turquoise. Instead, the industry standard for polishing turquoise is Aluminum Oxide (Linde A) or Zam.

  • Zam Polishing Compound: Zam is a green waxy compound containing aluminum oxide, specifically formulated for silver and turquoise.
  • Apply the Zam compound to a dry muslin or stitched cotton buffing wheel (do not use water).
  • Gently buff the dry turquoise cabochon against the wheel. The waxy compound fills in microscopic pores while the abrasive aluminum oxide brings the surface to a brilliant, high-gloss shine.

Warning: Do not generate too much heat on the buffing wheel. Excessive heat can cause the epoxy resin in stabilized turquoise to melt, smearing across the face of the stone and ruining your polish.

With clean water, light pressure, and the right buffing compound, cutting turquoise is a fast, satisfying process that results in some of the most iconic jewelry pieces in the world.