6 Factors to Consider in Selecting Fine Mineral Specimens

6 Factors to Consider in Selecting Fine Mineral Specimens

Of course, a specimen can also be beautiful and important simply because you enjoy its appearance. Still, the more knowledgeable you become about the factors which affect this perception, the better able you will be to identify and select fine quality mineral and crystal specimens. And the better the specimens you pick, the higher the quality level of your collection, and the more you will be able to enjoy it. Who hasn’t experienced disappointment when looking at specimens acquired as a novice collector? I certainly made mistakes back then, and I definitely don’t want to repeat them today.

The criteria listed below are my personal standards for selecting specimens for a display collection. I hope they will help you choose particularly worthy specimens for your personal collection from the millions available today at shows, on the internet, etc.

The dictionary defines beauty as: “The quality that gives pleasure to the mind or senses and is associated with such properties as harmony of form or color, excellence of artistry, truthfulness, and originality.” We all know that beauty is in the eye of the beholder, so what is perceived as beautiful will vary from person to person. Nevertheless, when looking at a mineral specimen, there are some elements of beauty that are pretty universal. For example, how are the crystals placed on the specimen? Are they grouped nicely?

A beautiful red quartz specimen from Fujian, China

Are they presented in a balanced fashion? Or, are they crowded together, all on one side, or too near the top or bottom? Are they of varying sizes, proportional to one another, or all one size? Is the color bright and appealing, as appropriate for the species? Are individual crystals sharp and well-defined? Do the crystals and matrix relate well to each other in size, ratio and form? Does it have an attractive composition, with a pleasing sculptural or architectural feel to it, with appealing three-dimensional viewing angles? Do the crystals interact with space in a pleasing way?

Prase quartz from Serifos Island in Greece - an excellent example of the beauty of crystals interacting with space

Just like viewing a work of art, these highly subjective factors contribute to the perceived beauty of a fine mineral specimen. This perception results from a pleasing aesthetic arrangement that appeals to your eye, and plays a major role in the pleasure you get from looking at a specimen.

2. Color & Contrast
It’s simple: Vivid colors catch the eye and make a high-impact visual impression. So, minerals with bright, highly saturated, intense colors are naturally more desirable than white, black, or gray minerals.

Keep in mind that lighting makes a huge difference in how the eye perceives color. Specimens viewed in sunlight almost always look significantly different (better) than when viewed in fluorescent, incandescent or halogen light. A customer once wrote, concerned about the lack of yellow color in a citrine crystal she purchased from us. I suggested she take it out in the sun to see its true color. She wrote back that the color was great, but that she was still disappointed that it didn’t look that color in her display cabinet! Confusion over this issue prompted us to include a link in all our listings to an article detailing what we do to ensure accurate color representation in our photos (click here to read the article). To sum it up, we recognize sunlight as the universal standard that everyone, anywhere in the world, can use to judge color in a mineral specimen. That’s why we use TruColor lighting that is as close as possible to 5000º Kelvin, which is the color temperature of sunlight. You might consider using similar lighting in your display cabinet to show off your minerals at their best.

The mesmerizing, brilliant red color of crocoite from Tasmania.

Another physiological factor is that the eye sees colors differently depending on what color they are seen with. You may recall the arrangement of color opposites on the color wheel from your school days: green is opposite red, orange vs. blue, yellow vs. purple. When viewed side-by-side, color opposites both appear to be more vibrant, intense and saturated than either color alone. This is the principle behind color contrast. Similarly, light colors set on dark colors appear brighter and more vivid, and also clearly define crystal edges and enhance three-dimensionality, thus making the specimen more appealing to the eye.

Prenite with epidote, showing the appeal of dramatic contrast

Another form of contrast is that between the crystals on a specimen and a duller matrix. Neophytes sometimes ask how to get the crystal out of the rock, but the fact is that a specimen on or in matrix is far more interesting and appealing (and has more scientific value) than a loose crystal.

The late Marvin Rausch built a world-class collection by specializing in high-contrast mineral specimens, such as red rhodochrosite on blue fluorite from the Sweet Home mine, green prehnite on near-black epidote from Massachusetts, and more. Though he had only 600 specimens in his collection, about 50 of them had graced the covers of a major mineral magazine, and the rest were selected for their intense colors. You could do worse than following his lead!

3. Luster & Transparency
Luster is a description of the way in which light interacts with the surface of a crystal. There are 10 commonly used terms to describe luster (or lustre):

  • Adamantine – the brilliant look of very gemmy crystals (diamond)
  • Dull - a non-reflective surface of any kind (feldspar)
  • Earthy - the look of dirt or dried mud (psilomelane)
  • Fibrous - the look of fibers (asbestos)
  • Greasy - the look of grease (opal)
  • Gumdrop - the look a sucked on hard candy (stream-worn gemstones)
  • Metallic – the look of opaque and highly reflective crystals (pyrite)
  • Pearly – the look of the inside of a mollusk shell or a shirt button (talc)
  • Resinous – the look of crystals with a golden, soft sheen (amber)
  • Silky - the look of silk, similar to fibrous but more compact (fibrous malachite)
  • Submetallic – the look of a poor metallic luster, opaque but reflecting little light (sphalerite)
  • Vitreous - the look of glass - the most common luster (quartz)
  • Waxy – a fairly dull look, as if coated with wax (jade)
Quartz - an example of vitreous luster

Because reflected light is highly appealing to the eye, specimens which have the glint of light from a cut diamond or the gleam of gold are perceived to be more attractive than those with dull surfaces. Transparency, which is closely related to luster, is highly desirable in the crystals on a specimen.

A gemmy heliodor crystal showing excellent transparency

“Gemmy” or “gem” crystals are so called because they have a cut gemstone-like appearance. Since the earliest times, people have been fascinated by the unique properties of a solid object that is transparent. At least part of this attraction is that light shining through a crystal creates a luminescent glow which the eye finds mesmerizing.

You can’t get around this fact: damage is damage is damage (and more often than not, even the appearance of damage is damage). Damage can range from infinitesimal, barely visible wounds (called “Wilburs” after world-class collector Dave Wilbur), to dings, bruises, nicks, breaks, internal fractures, cleaves (breakage along natural cleavage planes), contacts (where a crystal grew against another crystal), and broken off, missing crystals. I have yet to see a mineral specimen that is truly perfect, though there are a select few that are nearly so. Realistically, some degree of compromise is required – especially for those without the financial resources to spend hundreds of thousands of dollars for a world-class specimen. My main rule is that if damage is really noticeable and interrupts my enjoyment of the specimen, then I don’t want it. That being said, I consider where the damage is (e.g., off to the side is better than smack dab in the middle). I also consider the rarity of the mineral: damage on amethyst is unacceptable because there’s so much of it available, while I might be willing to live with it on a kammererite specimen because this mineral is so rare.

What about saw marks on the bottom or back of a specimen? Purists avoid these, preferring a “natural” specimen. But who’s fooling whom? A well-placed saw cut can turn an average specimen into an excellent one, whether by cutting off damaged areas, by achieving a better balance between crystals and matrix, or by giving a specimen an enhanced orientation that displays the crystals just so. And, using today’s equipment and techniques, saw cuts can be disguised so well that they look just like natural breaks and become “invisible”.

Though repaired, this world-class cerussite crystal from Tsumeb is still a very desirable specimen

Finally, there’s the question of repairs and reconstruction/restoration. Due in part to the outstanding restoration work performed on Sweet Home rhodochrosite by Bryan Lee’s crew, most collectors no longer consider a repair an automatic deal-breaker. The sky high prices of the Sweet Home material, and their escalating values since the mine was closed, have proven that invisible or near-invisible repairs do not automatically negate the investment value of a specimen. And sometimes repair is the only way to preserve a really significant specimen of great value or rarity.

5. Crystal Size, Quality, Form and Definition
Large, perfect crystals are rare, and are thus more desirable to a mineral collector than smaller, imperfect crystals of the same species. It’s only human: almost everyone wants to own the biggest, the brightest, or the best “shiny objects”. Mineral collectors are no different. On the other hand, keep in mind that while a 6” tourmaline crystal is rare and thus more valuable than a 3” one, a near-perfect, transparent 3” one is more appealing than a larger one that is flawed.

Who says size doesn't matter in a quartz crystal?

In addition to size, other factors to consider are a crystal’s sharpness, definition, form, and the quality of the termination. Cleanly defined edges, without rounding or irregularity are highly prized. Picture-book, classic terminations that are symmetrical, attractively shaped, and in proportion are more desirable than ones that are irregular or overly complex, because they add to one’s enjoyment of a specimen, rather than distracting from it.

Always buy specimens that are a joy for you to behold. Almost ten years ago, when we were set up to sell Wise Mine fluorite at the Inn Suites in Tucson, a customer came in to look around. I asked him what kind of minerals he collected, and he said, “I’m a lightning-bolt collector.” Seeing my perplexed face (I was thinking fulgurite), he said, “Yes, I buy specimens that strike me like a bolt of lightning.” He had it exactly right. He would only buy specimens that have what Stuart Wilensky calls the “Wow Factor”. Wilensky says this is the most important criteria, and the least scientific. It’s a double whammy: a powerful gut feeling combined with a mighty wallop to the naked eye.

This Brazilian quartz crystal actually was struck by lightning! ;)

Bryan Lees of Collector’s Edge Minerals uses a dramatic, theatrical approach when showing a fine mineral specimen to a discerning collector. He leads the buyer into a darkened the room, uncovers the specimen, then turns on specially arranged brilliant lighting set up in advance to create a powerful visceral and visual impact. To test for this phenomenon yourself, just note your own reaction when you first see a specimen in person. If you exclaim, “WOW!,” then all the other criteria are probably just icing on the cake.