how do they cut diamonds into shapes?

Diamond cutting is a highly precise art and science that transforms rough diamonds into dazzling gemstones. The process involves multiple steps and techniques, which can be categorized into traditional and modern methods. Below is a detailed introduction:

 

Traditional Diamond Cutting Techniques

• Cleaving: Cleaving involves splitting the rough diamond along its natural cleavage planes using a sharp blade. This method dates back centuries and is crucial for dividing rough diamonds into smaller pieces for further processing. A diamond cutter must carefully analyze the rough diamond's crystal structure to determine the optimal cleavage plane. With a precise strike using a steel blade, the diamond is split into sections suitable for cutting. Cleaving is typically used for large, well-formed rough diamonds with clear cleavage planes.
• Sawing: Sawing is used when the rough diamond lacks natural cleavage planes or when the desired cutting location does not align with a cleavage plane. The cutter uses a phosphor bronze blade rotating at approximately 15,000 rpm. Despite the use of a diamond-coated blade, the hardness of the diamond makes this process time-consuming, often taking several hours to complete. Modern sawing machines may also utilize diamond-coated circular saw blades or laser saws.

 

Modern Diamond Cutting Techniques

• Laser Cutting: Laser cutting technology uses focused beams of light to cut diamonds with incredible precision. It offers higher accuracy and efficiency compared to traditional methods, reducing waste and enabling the creation of complex designs. Laser cutting allows diamond cutters to produce intricate shapes and patterns, and the precision of the cuts ensures that every facet is aligned perfectly to maximize the diamond's brilliance and sparkle.
• Bruting: Bruting is a modern diamond cutting method primarily used to shape diamonds into round forms. It involves mounting two diamonds onto rotating spindles that spin in opposite directions. The diamonds are ground against each other to gradually shape the edges into a perfect circle. Bruting requires significant skill and patience to ensure proper alignment of each facet, enabling light to reflect and bend beautifully within the diamond. This method is particularly important for creating round brilliant cuts.
• Polishing: Polishing is the final and most critical step in the diamond cutting process. It involves carefully smoothing and refining each facet of the diamond to achieve maximum brilliance and sparkle. Polishing is divided into multiple stages. Initially, coarser abrasives are used to remove surface roughness from the diamond. Subsequently, finer abrasives are applied to polish the diamond's surface to perfection, resulting in a flawless, mirror-like finish. Polishing enhances the diamond's aesthetic appeal and value.

 

Other Diamond Cutting Techniques

• Blocking: Blocking establishes the diamond's basic symmetry by creating the first 17 or 18 facets. For smaller diamonds, the process may stop here. However, larger diamonds proceed to a specialist brillianteer for additional facet polishing to enhance brilliance and fire. During blocking, a skilled craftsman presses the diamond against a high-speed rotating wheel (spinning at 3,000 rpm) to grind it into its preliminary form, forming four main facets: the crown, pavilion, table, and culet. This stage focuses on maximizing the diamond's weight while setting the angles for optimal light reflection.
• Brillianteering: In this stage, minor facets on the crown and pavilion are added and adjusted to maximize the diamond's light return and beauty. The diamond is mounted on a rotating arm and polished using a spinning wheel to create smooth, reflective facets. The number of facets depends on the original structure of the diamond and the desired cut. For example, a round brilliant cut typically features 58 facets (including the table and culet). Other cuts, such as emerald or oval, have unique facet arrangements. Each facet is meticulously placed to enhance the diamond's light performance.

 

Diamond Cutting Process

• Planning: The first step is analyzing the rough diamond to determine the best cut to maximize its sparkle, weight, and overall beauty. Advanced software is used to map out the ideal cut. A highly experienced cutter, known as a marker, considers various factors such as the diamond's size, shape, clarity, and crystal direction to decide whether to saw or cleave the rough diamond and marks the cutting locations. This step may take months for large, expensive gems.
• Cleaving or Sawing: Depending on the plan, the rough diamond is either cleaved or sawed. Cleaving splits the diamond along its natural grain using a precise strike with a steel blade. Sawing, on the other hand, uses a diamond-coated saw or laser to slice the rough diamond into smaller pieces for further cutting. Lasers are particularly useful for cleaving thin or "included" diamonds (those with microscopic flaws) and for inscribing microscopic identification marks on finished gems.
• Shaping: This involves creating the diamond's preliminary shape. For round diamonds, bruting or girdling is used. A computer-controlled bruting machine spins diamond against diamond to form a rough round shape. Faceting follows, where flat surfaces are cut into the diamond to reflect and refract light, creating brilliance and sparkle. The most common faceting style is the round brilliant cut, which features 58 facets. Other cuts like emerald or oval have their unique facet arrangements.
• Polishing: The final stage of diamond cutting. The diamond's facets are polished to ideal proportions and perfect symmetry to maximize the reflection of white light. Polishing is also known as brillianteering. The diamond's final facets are polished to enhance its brilliance, fire, and scintillation. The polished diamond is then inspected for symmetry, proportions, and quality.
• Quality Control and Inspection: After the diamond is cut and polished, it undergoes strict quality control and inspection to ensure it meets high standards of symmetry, proportion, and finish. Only diamonds that pass these inspections qualify as finished gemstones ready for setting into jewelry or other applications.

 

Diamond Cutting Tools

• Cleaving Knives/Saws: Specialized knives or saws with diamond-coated blades are used to make the first cut on the rough diamond. Jewelers often split the gem along its natural grain lines to minimize waste.
• Bruting Machines: Traditional bruting was done by hand, but modern bruting machines use two rotating spindles with diamonds mounted on them. As they spin in opposite directions, the diamonds grind against each other to form a round shape. Modern bruting machines are computer-controlled for maximum precision.
• Lasers: Lasers have become increasingly important in diamond cutting. They can cleave thin or flawed diamonds and inscribe microscopic identification marks on finished gemstones.
• Diamond Polishing Wheels: After the diamond is bruted into a round shape, it is polished on a wheel containing diamond powder to achieve its final brilliance and shine.

 

Diamond cutting is a complex process that combines artistry and science. It requires extensive training and expertise. Even minor mistakes during cutting can significantly impact the quality of the final gemstone. With advancements in technology, modern diamond cutting techniques have greatly improved the precision and efficiency of the process, enabling the creation of more flawless and valuable diamonds.