Trimming Mineral Specimens
GETTING RID OF extra matrix, or removing unattractive parts of the specimen will enhance your pieces, sometimes turning an ordinary piece into a real show piece. It takes study and courage, but the rewards are worth it.
A use for leaverite
Ever wonder what you are going to do with all that leaverite and trashite you hauled home in your early collecting years and haven't gotten rid of yet? Well, you could use some of it to learn something about trimming specimens. After reading this article, try trimming out a crummy pocket of broken crystals, just to get the experience!
Start in the field
Trimming usually begins in the field where you find the specimens. See our friend in the photo? He is doing some serious trimming!
I usually carry a 8-pound sledge hammer and a 4-pound crack hammer with me wherever I roam. (See also collecting tools) These are generally sufficient to get the specimen down to a size that I can bring it in from the field. Also, many materials will not hold up to this type of trimming (the shock from the hammer blows break the crystals loose from the matrix) so it becomes evident that only through experience will you learn what can stand up to collecting and what to leave for someone else to waste their time and energy on. A knowledge of the matrix and its peculiar nature is essential. You will ruin some specimens learning how to trim, but hopefully, you will also learn how to greatly improve some of your specimens.
An expensive lesson
An example that taught me a lesson concerns a nice thumbnail of bright yellow paper thin wulfenite blades that I paid $40 for. The matrix was too large for a perky box so I thought that if it would trim to fit, I would have a $100 thumbnail for my efforts. Well, I used a pair of ceramic tile nippers. The shock generated when the matrix popped shattered the wulfenite into a hundred pieces. All this happened because I was not experienced in trimming that type of specimen and host rock. The lesson: don't work on a good quality specimen until you have the experience gained from trimming some average quality samples.
Trimming tools to use
There are many tools that can be used to trim specimens. You are only limited by your pocketbook. Simple hammers, chisels, and tile trimmers may be supplemented by screw-type pressure trimmers, hydraulic pressure trimmers, and/or diamond saws. (Note: a peculiar trait of veteran mineral collectors is that they really dislike a saw cut surface on a specimen, so if you must use a saw for trimming, be prepared to take some flack from some collectors) Never trim a specimen just to make it set up nicely. You can always get a stand to accomplish this goal.
Shock is the great enemy of any specimen. Anything that can be done to reduce shock will give you better odds of accomplishing your task. I once cradled a cabinet-sized specimen in my lap and held it with leather gloves as tightly as possible while a companion trimmed over half the matrix off with a 4-pound sledge hammer. The weight went from about 15 pounds to about 8, while the wholesale value went from $225 to $650! It was scary work and took about 10 minutes of concentrated effort, but was a most interesting experience. The collector, an expert in trimming this material, had saved the piece for almost a year because he knew I would be trusting enough to help him, and because he could not do this by himself.
The purpose of trimming is to remove excess material to improve the overall quality and to remove damaged areas detracting from the overall esthetics of the piece, thus improving the value of the specimen. If you cannot accomplish these goals, then do not trim it.
Matrix vs. crystals
Matrix has its own properties, independent of the minerals you desire to collect. It may be soft and punky, brittle and highly fractured, compact and hard as the hinges of hades, uniform and predictable, or any combination of these characteristics. Keep in mind the strength of the crystals you are trying to recover. Are they brittle or do they cleave easily? Are they firmly attached or about ready to fall off? These properties (of both matrix and crystals) you can quickly learn from a poor quality specimen by tapping on it with a regular rock hammer.
I can not tell you which specific method to use because I cannot possibly know the characteristics of every specimen. But I can make a few recommendations. Then it's up to you to try, and through your efforts, gain the necessary experience.
Two kinds of matrix
I deal mostly with 2 types of matrix: hard and uniform that is somewhat brittle, and softer and highly fractured. The former is relatively easy to work with and the latter much more difficult.
When I work with hard and uniform matrix, I often am trying to extract a pocket of crystals from a very large host rock. I start in the field with an 8-pound sledge to remove bulk from the piece. I work away from the pocket, but not opposite it since the shock would carry straight through the matrix and to the crystals. Once it is down to a reasonable size, depending on the scarcity of the types of crystals, I either work it on down with a 4-pound hammer or wrap it up to take to my prep area at home where I can take more time and work under a more controlled environment. There I may use a pressure trimmer or chipping hammer to remove the remaining excess host rock. If the boulder is too large to work effectively with an 8-pound hammer, then I get serious around the edge of the pocket with a hammer and chisel. I often recover as a couple of miniature specimens the best portion of a crystal pocket that otherwise is impossible to collect. These specimens I handle very carefully and wrap with toilet paper (one of the cheapest and handiest wrapping papers ever invented!). Many times I have nothing else to do with these pieces other than to clean them.
Soft and fractured matrix
Soft and/or fractured matrix is a completely different situation. You must carefully examine the entire piece. If one crack goes through the pocket, then you are apt to split the specimen. If not, then light tapping on the back side, with your strokes going parallel to the long direction of the pocket (definitely not at right angles to the pocket) give you the best chance to chip away excess material.
Pressure trimmer a boon
On some specimens of either type of matrix, a pressure trimmer is essential. The effectiveness of this type of trimmer comes from the highly directional planar pressure (pinch) it generates in the matrix.
Several brands of small screw-type trimmers are available. The size of specimen you can trim is limited by both the distance between the vertical rods, the length of the rods, and the strength of the matrix you want to break. If too tough, you could strip the central screw's threading. So, you have to use common sense or you will ruin the machine.
A C-clamp type trimmer, either screw feed or hydraulic, is available on the internet at: http://www.rocktrimmer.com The smaller one is around $70 plus postage and the larger hydraulic one is around $550 plus shipping. Additional similar C-clamp and I-beam type trimmers are available at: http://attminerals.com/equipment.htm
Know when to quit
The final trick of trimming comes from knowing that you have done everything you possibly can to improve the specimen and that it is time to quit. I have witnessed some extremely poor examples of trimming and some spectacularly successful ones. One example concerns a wavellite specimen purchased from a local dealer at Mount Ida by a University professor. He agreed to let a friend, known for his trimming expertise, remove some matrix right at the guy's shop. One whack and the specimen was only 1/3rd as large and probably worth 5 times what the prof paid for it.
In another example, a friend loaned me a spectacular variscite specimen for a display. I noticed that a small knob on the backside of the specimen appeared to be loosely attached. One tap on that knob to remove it and the specimen split in half! Fortunately for me, most of the mineralized portion was on one half, having not split down the middle of the cavity. The lesson? No matter how much experience you have, never try trimming someone else's specimen without their permission!