Canadian Rockhound: The Centennial Cut

The British Columbia Faceters' Guild was formed in 1963 so that faceters, beginners and advanced, could get together to exchange ideas regarding faceting equipment, cutting and polishing of gem stones, field trips, and displaying the finished precious gems.

To become a member of the British Columbia Faceters' Guild a person has to facet one gem stone. To stay a member at least three gem stones have to be faceted in one year. This created a very active club.

Not all members had faceting equipment, but any person who wished to join the British Columbia Faceters' Guild could go to the various members who had equipment and with some instruction could facet a stone. This encouraged new members to obtain their own faceting equipment. Members of the guild designed and made fourteen faceting machines.

One of the projects of the guild was to facet a famous diamond replica. The name of the famous diamond was placed in a box and the members drew one name and promptly went to work. In a very short time many beautiful replicas were finished. Many of these replicas were quite large, presenting quite a challenge in cutting and polishing. These replicas were on display at the annual British Columbia Gem & Mineral Show [organized by the Lapidary Rock & Mineral Society of B.C.], which attracted a great deal of attention.

Centennial cut profile

The Centennial cut is different in that it has no flat table, but has 16 facets at 10 degrees. The girdle, instead of being two percent the total depth of the stone, is 2 mm wide, with 85 degrees and 95 degrees alternating instead of the usual 90 degrees. With this table and girdle, a very brilliant gem was created. Indexing is for a 64 index gear. Angles are for quartz.

Cut the crown first, the pavilion last.

Crown:

Grind 16 girdle facets at 90 degrees;
Index: 64 - 4 - 8 - 12 - 16 -
20 - 24 - 28 - 32 - 36 - 40 -
44 - 48 - 52 - 56 - 60
Grind 16 facets at 42 degrees;
Index: 64-4-8-12-16-
20-24-28-32-36-40-
44-48-52-56-60
Grind 8 girdle facets at 85 degrees;
Index: 64-8-16-24-32
40-48-56
Grind 8 girdle facets at 95 degrees;
Index: 4-12-20-28-36-
44-52-60
Make a straight line on crown girdle edge.
Grind 16 facets at 38 degrees;
Index: 62-2-6-10-14-
18-22-26-30-34-38-
42-46-50-54-58
Grind 16 facets at 23 degrees;
Index: 64-4-8-12-16-20-
24-28-32-36-40-44
48-52-56-60
Grind 16 facets at 10 degrees;
Index: 62-2-6-10-14-
18-22-26-30-34-38
42-46-50-54-58

Polish crown facets in this order: Nos. 7 - 6 - 5 - 2 - 3 - 4

Pavilion:

Grind 16 facets at 42 degrees;
Index: 62-2-6-10-14-
18-22-26-30-34-38-
42-46-50-54-58
Make the girdle 2 mm wide.
Grind 16 facets at 75 degrees;
Index: 64-4-8-12-16-
20-24-28-32-36-40-
44-48-52-56-60
Grind 32 facets at 43 degrees;
Index: 1-3-5-7-9-11-
13-15-17-19-21-23-
25-27-29-31-33-35-
37-39-41-43-45-47-49
51-53-55-57-59-61-63
Grind 16 facets at 40 degrees;
Index: 64-4-8-12-16-20-
24-28-32-36-40-44-48-
52-56-60

Polish pavilion facets in this order: Nos. 4 - 1 - 3 - 2

Tables:

Pavilion - Table

This article may not be copied, distributed or reprinted in any form without the Canadian Rockhound editor's permission. The author is now deceased. To contact the editor, please use the e-mail address provided. Authorized reprints must acknowledge the author, original source and the Canadian Rockhound, and include the website URL address of the Canadian Rockhound.

The preceding article was originally published in the February 1967 issue (Vol. 11, No. 1) of the Canadian Rockhound, the official publication of the Lapidary Rock & Mineral Society of B.C., 1960-1980.