Amethyst 6x4 MM octogan Faceted Loose Gemstone, Amethyst is available in a wide range of millimeter (mm) sizes for jewelry, commonly ranging from small 3-5mm accent stones to large 10-20mm+ center stones. Standard oval cuts often include 6x4mm, 7x5mm, 8x6mm, or 10x8mm, while round stones are frequently 5-10mm. Large, high-quality faceted stones can exceed 18x13mm. Common Amethyst Size (mm) to Carat Examples (Faceted): 6x4 mm (Oval): ~0.24 - 0.66 ct 7x5 mm (Oval): ~0.45 - 1.00 ct 8x6 mm (Oval): ~0.8 - 1.55 ct 10x8 mm (Oval): ~2.50 ct 12x10 mm (Oval): ~5.05 ct 18x13 mm (Oval): ~10.65 - 14.2 ct 6.5 mm (Round): ~1.00 ct 8 mm (Round): ~2.00 ct 16 mm (Round): ~14.35 ct Other Formats: Beads: Common sizes include 4mm, 6mm, 8mm, and 10mm. Chips: Irregular sizes, such as 8x10mm. Octagon: Frequently available in 14x12mm for large rings Calibrated sizes (like 18x13mm or 10x8mm) are standard, making them easy to set in pre-made jewelry ...Read More