Koshu crystal and precious stones carving

Koshu crystal and precious stones carving Koshu suisho kiseki zaiku

Mesmerizing, delicate and expressive work
A brilliant encounter of natural gems and an artisan's passion


What is Koshu crystal and precious stones carving ?

Koshu crystal and precious stones carving called Koshu Suisho Kiseki zaiku in Japanese, are crystal and precious gemstone carvings produced in the city of Kofu, Yamanashi prefecture. Using traditional methods, natural gemstones are carefully cut, ground and polished to produce beautiful works of brilliant, colorful and transparent art, which last for a long time. Kofu has long been known for its abundance of crystal, which gave rise to the production of crystal artifacts and works of art. Koshu crystal carving is characterized by its extensive range of designs, including vibrant and lively animals, auspicious rising dragons, and charming modern characters much loved by children. The production process involves cutting, carving and polishing the crystal. Since the raw material is very hard, the grinding and cutting must be carried out very carefully as one slip can cause the crystal to shatter. A classic Koshu crystal carving technique is called yukanwhich is a technique to carve the crystal into chain-like shapes. To produce work of such delicacy and high quality, craftsmen with a good eye for crystal and command of the highest traditional techniques are necessary.


The origins of Koshu crystal and precious stones carving date back to the Heian period (794-1185), when crystal gemstones were discovered in the Mitake Shosenkyo Gorge and Mt. Kinpu area in the north of the Yamanashi Prefecture. Crystal was highly valued and was often revered as a religious object. During the period from 1830 to 1844, artisans were invited from the Tamatsukuri area in Kyoto to teach the techniques for hand-polishing gems to local people. The Koshu polishing technique of spreading emery powder on an iron plate, and smoothing gems by hand was established at this time, and ornamental items started to be produced. In 1876, Shiro FUJIMURA, the governor of the Yamanashi prefecture, founded a municipal crystal processing department in Kofu, and encouraged training by sending artisans to study at technical courses in China. Unfortunately, by the end of the Meiji period the crystal had run out and the following Taisho period (1912-1926) saw Kofu capitalizing on its advanced polishing techniques to become a center processing imported crystal, agate, diamonds, and other precious stones. Once facilities were electrified, the area took up production of gemstone components for precision machinery. After World War II, 80% of the production was exported. However, following the 1971 dollar shock, the focus changed to making craft products for the domestic market and by making full use of traditional techniques and modern technology, their overall quality as art works was improved.

General Production Process

  1. 1. Selecting gemstones The raw materials of Koshu crystal and precious stones carving are crystal, agate, jade, or tiger's-eye. It takes considerable time to cut, grind, and carve such hard stones. Crystal can be more than twice as hard as glass, so processing is very difficult. The wide variety of Koshu crystal carvings are a production of the skills, perseverance, and passion of the craftsmen. The first process of production is to select the rough stone among the dozens of stones. It takes years of practice to be able to select the stone that is the best quality for a piece. The gemstones are mainly imported and as there are various stones from crystals to agates and even diamonds, they need to select the stones while considering which polishing techniques to use to bring out the best of the stone. The skilled craftsmen also have the ability to sense any hidden flaws and natural features, such as scratches or mistiness.
  2. 2. Line drawing and cutting After the selection, the stone is cut to shape and inspected again for flaws. It is important to clearly ascertain the parts of rough stone that should be avoided in making a piece. Once the part being used is decided, draft lines are drawn and then cut with a powerful cutting machine along the lines.
  3. 3. Designing A draft picture is drawn on the cut stone while considering how to use the material feature. It is important to determine the most appealing feature part of stone for the focal points to design a crystal. For example, the focal point would be the face for the Buddha statue, so the stone will be designed to bring the best part to the face. Moreover, other parts including the shoulders, hands, and legs are drawn in detail to make the Buddha six heads high and well balanced.
  4. 4. Rough shaping A high speed diamond drill is used to cut along the draft lines and give a rough shape to the work piece. One single slip and the work can be ruined, therefore this is quite a difficult operation.
  5. 5. Rough scraping with the whet After the rough shaping, the stone is roughly scraped using a variety of high speed steel discs to give a finer shape closer to the final shape. The piece is scraped four times along with the whet using emery powder as a polishing agent. The emery powder used is coarse in the beginning and the grain becomes finer towards the finish.
  6. 6. Polishing The rough surfaces are polished using several different wooden discs. A hard wood disc is used in the beginning, followed by a soft willow or paulownia wood disc, and then a final polishing is processed with fine sand.
  7. 7. Finishing The last process transforms the natural rough gemstone into a work of art. A round whetstone and chromic polishing powder are placed in a rotary grinding machine. Then the stone piece is put into the machine and rotated until the required degree of shine is attained. Finally, the craftsmen give a final finishing to the detailed parts by hand with their highest skills.

Where to Buy & More Information

Yamanashi Gem Museum

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