Lapidary Honor

Arts & Crafts

Requirements

  1. Mention at least 4 safety precautions to take when sawing stones.

    Answer: Pelo menos 4 precauções de segurança ao serrar pedras: 1) Usar óculos de proteção, pois estilhaços e lascas de pedra podem atingir os olhos. 2) Usar luvas resistentes para proteger as mãos de cortes e do contato com a lâmina. 3) Manter a lâmina sempre lubrificada e refrigerada (com água ou óleo) para evitar superaquecimento, fratura da pedra e fagulhas. 4) Nunca colocar as mãos próximas da lâmina em movimento nem forçar a pedra contra o disco; alimentar a pedra devagar e com firmeza, mantendo as mãos afastadas do corte. — Lapidary work has a real risk of injury. Without goggles, quartz splinters can blind you. Cut-resistant gloves (kevlar) are standard. A dry blade heats up, deforms, and breaks — it can hit the operator. Fixing the stone in a vise avoids accidents with the hands. NR-12 of the Ministry of Labor regulates safety in cutting machines.

  2. Mention 2 types of lubrication and cooling for a diamond saw and what their purpose is.

    Answer: 1) Water — a common, cheap, and effective coolant for most stones. 2) Soluble oil (an oil+water mixture) — lubricates and cools better, recommended for intensive cutting. — Diamond blades reach 200-300°C without cooling — they lose their temper and break. Soluble oil keeps the saw cool and lubricated. Some stones (lapis lazuli, malachite) react with water — they require oil. A water system with a pump is standard in professional Brazilian equipment.

  3. Explain:
    • How a diamond saw cuts stones
    • How it loses the diamond
    • How it can be sharpened
    • What are the types of machines used for cutting stones

    Answer: 1) How a diamond saw cuts stones: the edge of the disc is impregnated with diamond particles (the hardest material that exists), which wear away the rock through abrasion as the disc rotates at high speed, usually cooled with water or oil to cool and lubricate the cut. 2) How it loses the diamond: through the natural wear of use, the diamond grains come loose or flatten out and the edge becomes smooth, losing the cutting capacity. 3) How it can be sharpened: by cutting an abrasive material (firebrick, sharpening stone, or aluminum oxide stick), which wears away the metal alloy of the edge and exposes new diamond grains, recovering the cutting power. 4) What types of machines are used for cutting stones: the trim saw for small, precise cuts, the slab saw for large cuts in blocks, and circular saws or grinders with a diamond disc. — Understanding how the disc cuts and why it loses its edge allows you to keep the equipment efficient and safe during lapidary work.

  4. Describe the 5 basic stages for polishing a stone or a flat surface.

    Answer: As 5 etapas básicas para polir uma pedra ou superfície plana: 1) Cortar/serrar a pedra na forma desejada. 2) Lixar com grão grosso (80-220) para nivelar e remover marcas de corte. 3) Lixar progressivamente com grãos médios (400-800). 4) Lixar com grãos finos (1000-3000) até a superfície ficar lisa e fosca. 5) Polir com composto de polimento (óxido de cério, óxido de estanho ou pasta diamantada) em disco/feltro ou couro, até obter brilho vitrificado (acabamento espelhado). — Each stage removes the scratches from the previous stage. Skipping grits results in scratches visible at the end. Hard stones (quartz, agate) require diamond grits. Cerium oxide is standard for polishing glass and silicate stones. Total time: 30 minutes to 4 hours depending on the size of the piece.

  5. What precaution should be taken between the sanding and polishing phase?

    Answer: Wash the stone and the equipment well between phases to completely remove the residues of the previous sandpaper. Coarse particles mixed with the fine phase cause scratches that are impossible to remove. — Cross-contamination between grits is the most common error in amateur lapidary work. A single 80 grit mixed in the polishing paste scratches the entire piece. Professionals use different cloths for each grit. Washing between phases can take 5-10 minutes but prevents hours of subsequent corrective rework.

  6. What is a template and how is it used?

    Answer: A template is a rigid mold (metal, plastic, or MDF) with a predefined shape (oval, round, teardrop) used to mark the outline on the stone before cutting. — Professional templates come in sets with several standard cabochon shapes (10x14, 13x18, 18x25mm). Marking with a graphite pencil does not work (it washes off with water); use an appropriate pen. Templates are especially useful for making identical pairs (earrings, cufflinks). Reusable indefinitely.

  7. What is a cabochon and what is the thickness of the slab it is made from?

    Answer: A cabochon is a stone cut with a rounded top surface and a flat base (without facets). Standard slab thickness: 4-6mm for medium cabochons, 6-8mm for large ones. — Cabochon comes from the French caboche (head). Unlike faceted stones (diamonds, sapphires), the cabochon has a smooth convex top. A thickness below 4mm is fragile; above 8mm is disproportionate. Opaque stones look better as cabochons because they do not need transparency or light refraction.

  8. How do you decide the best angle and/or position for polishing a stone?

    Answer: Evaluate the stone by the angle of the crystalline structure (hardness varies by direction), the visual pattern (color vector, stripes), defects (keep fissures away from the outer surface), and the final function (ring, pendant). — Stones like agate have bands that should be parallel to the base. Quartz has a crystallographic orientation that affects polishing. Visible defects should be in hidden positions (behind the piece). Experienced lapidaries 'read' the stone before cutting — the positioning decision defines the entire work.

  9. Mention at least 2 methods of wet sanding to shape and polish a stone.

    Answer: 1) A rotating diamond disc with a constant flow of water — for cutting and fast coarse sanding. 2) Manual wet sandpaper on a rubber block — for finishing and fine adjustments. — Wet sanding avoids the accumulation of stone dust (silicosis if inhaled). Water lubricates and cools. Wet sandpaper has grits glued to waterproof paper (220 to 5000). A tumbler is automated — it spins for days with stones + grit. Professional tables have 6-8 basins with progressive grits.

  10. What materials are polishing compounds made of?
    • If a scratch appears during polishing, how is it removed?

    Answer: Compounds: cerium oxide (glass and quartz), tin oxide (all stones), chromium oxide (greens), diamond paste (extreme hardnesses), tripoli (finishing). — Cerium is the most common (costs R$ 30-100 per kg). Tin is versatile. Diamonds in paste range from 1 micron to 50 microns. Tripoli is traditional for metals. A scratch in the polishing phase always comes from cross-contamination — going back 1-2 phases is necessary. Do not try to polish more to 'erase' the scratch.

  11. Demonstrate how to saw and rough out a rough stone. With a cabochon, through the stages of grinding, sanding, and polishing to a high shine or glassy finish, finish the stone.

    Answer: Saw the rough stone with a diamond saw (water as lubricant), rough it out with a coarse abrasive disc, grind the cabochon shape to the template line, sand progressively (220→3000), finish with a polishing paste (cerium/tin) on a felt disc until shiny. — A cabochon takes 1-3 hours for an amateur. The saw holds the stone firmly; without holding it with the hand. Roughing out removes excess material. Grinding adjusts the exact shape. Progressive sanding eliminates scratches. The final polishing requires patience (10-20 min). The finished stone has a uniform mirror shine.

  12. Mount a cabochon on some type of support, such as a wooden pin, a sewing pin, a keychain, etc., with cement.

    Answer: Apply epoxy cement (Araldite or similar) to the base of the cabochon and fix it to the chosen support (pin, pin, keychain). Press firmly for 5 min, let it cure for 24h. — Two-part epoxy (resin + hardener) is the best cement for amateur jewelry. Complete curing in 24h. Apply a small amount — excess leaks out the sides. For a keychain, a smooth metal base accepts cement. Ready-made settings (with a silver bezel) are a professional alternative without cement.