Canadian Rockhound: Ammonite Jewellery

Ammonites are a group of extinct cephalopods (squid-like animals) that existed on earth for about 330 million years. Alberta, Canada, is the only known source of the fine gem quality variety. Photo courtesy The Stone Company, Š1996.

Ammonite Jewellery
By Chester Miller

Ammonite, with its beautiful flashes of red, green, orange and purple, rivals the finest Australian opal when fashioned into wearable jewellry. The process is more demanding than making an agate or chrysoprase cabochon but the results are definitely worth the effort.

Ammonite, being relatively soft in comparison to other gemstones, requires a protective surface, and in some cases, because pieces are so thin, they must be backed with a more durable material, thus making a doublet or triplet, as the case may be. In this article I will describe the procedure I use to make ammonite jewellry.

Lapping

After choosing a piece of ammonite, the area to be on top is flat lapped on either a 180 or 200 grit diamond lap. If the piece you are working with has sufficient "mud" on the underside, it can be flat lapped and used as the base. If the piece is very thin, it will be necessary to lap both sides as it is advisable to apply a thin slice of harder material for the base. I use black basalt, applied with 5 minute epoxy. No special care in gluing is needed here as long as it is securely fastened.

Though ammonite is colorful, it is soft and the top of stone needs to be protected. This is done by applying a slice of quartz to the upper side. Man-made quartz is ideal for this purpose and less expensive than optical quality natural quartz. The thickness of the quartz slice can be a personal choice, anywhere from 1/16" to 1/8" or more if preferred. More thickness gives greater magnification which can be desirable, depending on setting chosen for finished piece. This must also be flat lapped on side to be fastened to the ammonite. If preferred, pre-finished quartz cabs in calibrated sizes are also available from gem dealers.

Fastening the pieces

Choose an object to raise a working surface above the level of your desk or table, such as a brick. Cover this with waxed paper. Material needed to fasten pieces together are Opticon and Epoxy 330. Clean both slices with acetone and place on the brick. Put the Opticon and Epoxy on or near the brick, place all this under a desk lamp for approximately an hour to warm both slices and materials.

The next step is to put a generous amount of Opticon on the ammonite slice, leave under lamp from 2 to 4 hours. Use only Opticon A - do not mix with hardener. Note: The hardener in Epoxy 330 also hardens the Opticon. It is for this reason no hardener is used when applying Opticon.

After this, using the straight edge of some object, (credit card or similar hard card works well) scrape off the excess Opticon.

The following directions should be followed closely:

Place two parts of Epoxy 330 on a flat surface (piece of glass or a tile). Do not stir! Using a round toothpick, carefully roll the toothpick back and forth through both parts of the epoxy to thoroughly mix the two parts together, making sure not to lift the toothpick off the surface, as this could create bubbles. Now, holding the ammonite slice by the edges only, apply mixed epoxy . If any bubbles are detected these can be punctured with the end of a toothpick, or carefully lead them out to the edge of the slice. Again, holding both pieces by the edge, starting at one corner, gradually lower the quartz piece onto the ammonite and lightly press the pieces together without sliding or moving pieces.

At this stage some of the excess epoxy can be placed on the quartz top. This allows you to see if any bubbles were trapped. (This can be removed in a later finishing stage).

If no bubbles are found, allow the ammonite piece to dry for 24 hours. However, if bubbles were obvious, you must start over, using acetone to clean all pieces.

Final steps

After the drying period, your ammonite piece can be worked as for any cabochon: shaping, sanding and polishing the top part prior to setting in a finding of choice, or fabricated finding, if making irregular shaped stone.

Ammonite Jewellry

A finished piece of ammonite jewellry.

– Chester Miller is a lapidary artist and a member of the Delta Rockhound Gem & Mineral Club in Delta, British Columbia.

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