When evaluating collectible minerals, you must keep in mind a series of characteristics or factors without a standardized scale for each one of them, which is why prices don’t correspond with tables, but they respond to the buyers’ interests, in this case collectors in general, and to the availability the salespeople may have of the mineral.
Below we will describe some of the main aspects taken into account by professionals and collectors, to place a value on minerals:
Mineral’s General State
A very important aspect without a doubt is the evaluated mineral’s conservation status, if the specimen has any damages, each of them will be analyzed and used as an argument to reduce the price. Son of the types of damages we can find are the following:
Bumps: A mineral that has any abrasions provoked by a blow or bump on the faces of the main crystal or secondary crystals can be dramatically devaluated. One of the moments in which blows most commonly happen are during the extraction of the minerals; most collectible minerals are obtained in mining projects of the industrial area or for the jewelry industry, where the care for the units’ integrity isn’t a priority. The transportation and storage of the minerals are also potential sources for damages, this is why a specimen in perfect state is very appealing and difficult to find.
Broken Crystals: Another one of the important defects is the presence of broken crystals in the specimens; as in the previous case, the process chain from the extraction up to the final collector is a source of possibilities for the crystals to break, especially the ones that are more exposed and generally very aesthetical.
Loss of Color: Some minerals are photosensitive and lose their natural color when exposed to solar or artificial light. A mineral that loses its color, loses a great portion of its value because the color is highly related to the beauty of the pieces.
Scratches: Sometimes minerals can resist a blow or rupture on its crystals, but friction with other minerals or diverse elements can cause unsightly scratches on the faces of the crystals that damage their value.
The crystallization and form of the specimens is a highly sought and valued factor in collectible minerals. The following are aspects related to the minerals’ crystallization and that dramatically influence their prices.
The Crystal’s Perfection: The perfection on the faces of a specimen’s crystals is directly related to the increase in its value. If it is a float crystal, it is very important that all its faces and edges are complete. If the crystal is in its matrix, it must have most of its body visible and in the best state of conservation possible.
Crystals with Complex Forms: Some crystals may have complex forms on their faces or in the crystal’s body in general, as a result of crystallization processes under very particular circumstances, which generate extraordinary specimens for their species, that make their value grow.
Figures on the Crystal’s Faces: Some crystals present striations, grooves or particular figures which, combined with a general good state of conservation wake a special interest in some collectors.
Crystal Twinning: Some specimens present a simultaneous growth of two or more twin crystals that create a crystal twinning. Well-conformed crystal twinnings and of uncommon species are very appealing and valued.
Size of the Crystal: Once the previous aspects have been reviewed we can affirm that crystals in the same conservation state and of the same beauty will have a higher value, the bigger they are.
One of the primary characteristics associated to the minerals’ beauty is their color. A specimen of an appealing and uniform color will always call for attention and will be highly valued. Some of the aspects to consider when we analyze the color of the minerals are the following:
Shade, Tone, and Saturation: Within a same mineral species, we can find the presence of different colors of their crystals; the ones with odder shades being the most wanted ones and, therefore, the ones with the highest value. The crystals that present a higher saturation and better tone are the most striking and highest-valued.
Discoloration: As we had mentioned in a section before, some minerals are sensitive to light exposure. Some exemplars like vanadinite that darkens and loses its shine or the realgar that loses its blood-red tone, turning yellowish, find their values affected if the specimens aren’t stored carefully.
Artificial Color: In some cases, an alteration of the mineral’s color is done to give the crystal an artificial beauty through heating processes, as happens with amethysts, which obtain an intense yellow color like the one of a high-quality citrine. Another practice we can find in the tainting market is the case of agates, which can result in very striking combinations of colors. In either of these cases, these color-altering processes should be noted to the buyer, who will evaluate if the change damages the mineral’s value, or increases it.
Dichroism: It’s a characteristic that is taken more into account by gemologists in minerals that are used to make gems, but some collectors appreciate this condition in minerals like tanzanite.
Presence of two or more colors in a crystal: There are very interesting cases in which a crystal presents two or more colors along its body, resulting in a great beauty. One of the most known cases is of tourmaline elbaite, which can be pink at its base, and green at the top of the crystal, between other color combinations. These types of crystals with combined colors are valued and desired.
Zoning: The zoning in some crystals can create specimens of great beauty. An example of this is the tourmaline known as watermelon that presents a pink or red color in its center, and green on the crystal’s walls.
The Crystals’ Transparency
This section applies to those varieties of minerals that can be transparent and can be a part of the evaluation done to the gems. Generally, those crystals that are completely transparent are of higher value, and from this point they will be evaluated according to the amount of inclusions, veils, fractures or milky aspects that the crystal may have, to reduce the price.
The importance of a crystal’s transparency lies in it allowing a bigger entrance of light and this heightens the natural color, making the exemplar be much more aesthetically appealing. The nature of the crystal that is going to be evaluated must be taken into account, because we can find some crystals that are very transparent, as it happens with quartzes, topazes, aquamarines, beryllium, phenacite, celestine, scapolite, among others and minerals that, though they are naturally transparent, present many inclusions like emeralds and tourmaline rubelite, in these cases, if the crystal is completely transparent, its value increases considerably.
Shine and Gloss of the Mineral
The shine is a characteristic that is closely related to the transparency because generally the most transparent crystals present smooth faces that enhance the entrance and exit of light in crystals. Another interesting concept is gloss, where light bounces off the mineral’s walls and generates a nice aspect of superficial shine, in this case the mineral can be interchangeably transparent or not. The shine and gloss, by enhancing the collectible minerals’ beauty, will positively influence their value.
The minerals’ rarity is a very important element in the determination of the commercial value because it follows in some offers the laws of supply and demand, if the mineral is rare, there will be very little availability in the market, and its value will increase according to its rarity and scarceness.
When we talk about rare minerals, we find that their production is very limited and that there are no new findings, or there are very few, as is the case of Colombian eucalses. Another rarity factor is uncommon crystallization for a given species that occurs in a particular reservoir and that the pattern doesn’t repeat itself in other places in the world. A similar case can happen with the color, we can see this in minerals like apatite, which can be extracted in different zones around the world, but the lilac colors of the Panasquiera mines in Portugal, or the pink ones of Colombia are highly esteemed due to their difficulty to be found between mineral dealers. We cannot forget to mention the minerals that are generally found in smaller sizes and therefore, when they are found in significantly larger sizes, are considered rare pieces that are hard to obtain; an example of this are emeralds, which are very infrequent in crystal sizes over 5cm conserving aesthetical elements previously mentioned like good color, transparency, adequate crystallization and with no damages; specimens like these are in the top of the most-valued and can reach very significant pricings.
We hope that when you’re looking for a new specimen for your collection, this brief summary can help you identify the main characteristics to keep in mind for a crystal. Remember it is not very probable you’ll find a unified price list for the different minerals, but reviewing the previous criteria you will be able to estimate if the price you have to pay is reasonable.