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 is a crystal and semi-precious gemstone carvings produced in the city of Kofu, Yamanashi prefecture. Using traditional methods, natural gemstones are carefully cut, ground and polished to produce stunningly beautiful works of brilliant, colorful and transparent art, which last for a long time.
From olden times, Kofu has 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 vibrantly alive animals, auspicious rising dragons, and charming modern characters much loved by children. The production process involves cutting, carving and polishing the crystal in the rough. Since the raw material is very hard, the grinding and cutting must be carried out very carefully as one slip and the work can shatter. A classic Koshu crystal carving technique is called yukan and means to carve crystal into chain-like shapes. To produce work of such delicacy and high quality requires craftsmen with a good eye for crystal and command of the highest traditional techniques.


The origins of Koshu crystal carving date back to the Heian period (794-1185), when crystal gemstone was discovered in the Mitake Shosen Gorge and Mt. Kinpu area in the north of the Yamanashi Prefecture. The crystal was highly valued and often revered as a religious object in its own right.
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 sheet, 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 carving are crystal, agate, jade, or tiger's-eye, and are mainly imported from overseas, although occasionally diamonds may be used. It takes considerable time to cut, grind, and carve such hard stones. It can even be more than twice as hard as glass. The wide variety of Koshu crystal carvings are a testament to the skills, perseverance, and passion of the craftsmen.
    The first process of production is to select the rough stone among the dozens of stones and it takes years of practice to be able to select the stone that is the best quality for a piece. The skilled craftsmen have the ability to sense any hidden flaws and natural features, such as scratches or mistiness. Also they know the best polishing techniques to bring out the hidden beauty of every stone.
  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 it has been decided, draft lines are drawn and then cut with a powerful cutting machine along the lines.
  3. 3. Designing with balance A draft picture is drawn on the cut stone within the consideration of 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, which would be placed on the great feature part of stone. Moreover, other parts including the shoulders, hands, and legs are drawn in details within making the Buddha in six heads high to keep the good proportion of the crystal piece.
  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 rough scraping will be conducted 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 the ever finer grades of emery powder. It is directed from coarse to very fine particles.
  6. 6. Polishing This step consists in polishing the rough surfaces using several different wooden discs. It is made from a hard wood disc, which is followed by soft willow or paulownia wood, and then a final rubbing up with fine sand.
  7. 7. Finishing The last process transforms the rough gem from nature into an aesthetic work piece. The round whetstone and chromic polishing powder are invested in a rotary grinding machine. Then the crystal piece is put into the machine and rotated until the required degree of shine is attained. Then the craftsmen give a final finishing to the detailed parts by hands with their highest skills.

Where to Buy & More Information

Yamanashi Gem Museum

See more Semiprecious stone craftwork

See items made in Yamanashi