New Mexico Mineral Symposium — Abstracts

The casting of meteorites to preserve their original character, especially before they are cut, is a well-known procedure. Casting of meteorites has been a part of museum operations through the years; Harvey Nininger, curator of meteorites in the 1930s, made reproductions of several meteorites. In an effort to improve replicas for exhibition, we have used scanned digital images of the meteorites' polished faces on the cut surface of the cast, which give a remarkably realistic appearance. This paper discusses this technique applied to the Rifle iron meteorite and two new stony meteorites from Weld County, Colorado.

The Rifle iron, originally a 226-lb mass, was found in 1948 about 6 mi northwest of Rifle, Colorado. It was sold to Harvey Nininger, and when he divided his collection in the 1950s, it was cut into two almost equal-sized pieces. The Denver Museum's piece weighs 100 lb and is about the size of half a watermelon. Recently we made a replica for the Rifle Creek Museum in Rifle, Colorado, which they placed on display May 28, 2003.

We applied the scanned-image technique to show the dramatic Widmanstatten pattern on the cut and polished face. The procedure for molding and casting the piece was traditional: several layers of latex rubber applied to the original, a plaster support jacket made, then plaster poured into the mold to make the cast. For our 100-lb Rifle meteorite, Chief Prep arator and Curator of Vertebrate Paleontology, Kenneth Carpenter, made the mold and poured the casts. Denver artist Helen Barndt painted the white plaster surface to look like the rusty brown iron meteorite.

Reproducing the beautiful Widmanstatten pattern on the cut and etched surface of the nickel-iron meteorite was a real challenge. Ken Erickson, department volunteer, made a high-quality, flat-field black and white photograph of the meteorite. This was scanned to create a digital image from which an inkjet photo-quality print was made. The gloss of the paper was matched to the gloss of the meteorite's surface.
After sanding and coating the flat surface of the cast with a grout and tile sealer, the image was glued to the cast with super ply-bond cement. The replica was carefully trimmed with a scalpel and touched up with paint.

This technique was also used by Jack Thompson on two other meteorites in the museum collection, both stony meteorites from Weld County, Colorado. One is a fairly fresh (unoxidized) ordinary chondrite found near Stoneham. It had been cut in two directions and shows well-pronounced internal structures including metal veining. The other, found near New Raymer, has a dark-brown oxidized color and an end piece cut off. The usual procedures for molding, casting, and surface painting were used as with the Rifle meteorite. However, these meteorites were small enough to be placed on a flatbed scanner, resulting in digital images for the cut surfaces. The suggestion for this method came from Wilson (2003). The scans were printed on photo-quality paper, and the images were glued to the flat surfaces on the casts, providing realistic exhibit-quality reproductions.

The meteorite from New Raymer was taken one step further because we did not get a chance to cast it before the end piece was cut off. The two ends were reassembled using cardboard shims and molding clay to make up for the space lost during cutting. A latex mold of the whole mass was made, and the casts were painted to look like the original. The final result is one cast with the shape of the original mass and another cast of the existing piece with the digital image of the interior on the cut surface. We believe that these projects are the first to use digital images on meteorite replicas.

References:

1. Wilson, W., 2003, Record-keeping for mineral collectors: Mineralogical Record, v. 34, pp. 210-212.