There are no exacting standards to determine the value of minerals. With experience, one can guess a mineral's price range by gathering certain information about the
specimen. Certain unique properties will set it aside from other specimens of the same
type. The important properties are:
- Color and Intensity
- Formation of Crystals
- Damage and Repairs
- Presence of Matrix
- Trimming and Cleaning
Color and Intensity
A specimen with a dull color does not stand out. Intense colors quickly grab the
eye and raise the value of a specimen. For example, the mineral Rhodochrosite
usually has a high value because its striking color.
In minerals that occur in transparent forms, the transparency level is important. The
greater the transparency and the more gemmy a mineral is, the more appealing it becomes, and thus increases its value.
Formation of Crystals
Almost all natural crystals will have minor imperfections or deformities. The larger a
crystal, the more it is likely to be deformed. Well formed or unique crystals will raise
the value of the specimen, especially if they are large.
Mineral specimens may contain damage or fractures that will decrease its value. Some specimens have been repaired with glue to repair a crystal or re-attach to a matrix. Although this is generally acceptable practice, the cost of repaired minerals are decreased and this information should always be disclosed.
The locality of a mineral's origin can be an important factor in its value. Mineral's from classic localities can be much more valuable then the same equal mineral from a more common locality.
The size of a mineral is important. Larger forms of a mineral will always command a premium, especially if they are well-formed and still have other positive attributes. Fairly large specimens, even of common
minerals, will usually have a higher value.
Luster is rarely a factor in mineral value, since the same type of minerals
exhibit similar luster among each other. There are a few cases where a specimen naturally
exhibits a greater luster than other minerals of its kind. This is especially the case in some minerals with a metallic luster. These exceptions give the
specimen a greater value.
Specimens of a mineral that exhibit unique, abnormal properties or are
intrinsically different than normal specimens of the mineral fall under this category.
Properties such as abnormal color, pseudomorphs, twinning, and odd crystals can give a
specimen extra value.
Presence of Matrix
Crystals in a matrix will generally be more valuable than similar
freestanding or floater crystals. A matrix shows the original uniqueness of the mineral and its formation.
Trimming and Cleaning
When minerals come out of the ground, they are usually dirty, coated, and in need of trimming. Proper trimming of a specimen or matrix can bring out the best in a mineral's aesthetics, which will increase its value. Proper cleaning and removal of undesirable coatings will also make a mineral more aesthetic and desirable. Minerals are sometimes soaked in acid or other chemicals to remove unwanted material or coating such as impeding Calcite growths and brown iron stains.
Some minerals are valuable due to their use as an important ore or for their use as a gemstone. For example, the silver ores may not necessarily look appealing, but demand a high price because of
their chemical composition. Some minerals such as the rare Phosphophyllite have become icons in the mineral trade, and are due to their rarity and insatiable demand command outrageous prices.
Rare minerals will be more valuable than more common ones. Fairly
common minerals, even if nicely colored and well formed, can be very affordable because of their
commonness (unless they are exceptional in other regards).
Minerals can sometimes be enhanced or repaired. Some examples include:
- Dyed, heated, or irradiated to intensify or enhance color
- Roasted or oiled to eliminate flaws and increase
- Cut to imitate well shaped crystals
- Glossed or polished with substances to enhance luster
- Glued to a matrix
- Wrongly labeled to fool collectors
- Glued together from a broken fragment
One should always look for these things when purchasing a
specimen. Many collectors consider repaired specimens acceptable as long as the repair details are disclosed by the dealer they purchase it from.