A repair means a human repaired the mineral, usually meaning broken pieces have been glued back together into the original growth form. Fragile minerals can break in the mining process, during shipping, or due to rough handling. Sometimes things just get dropped (ask me how I know 😭).

Unfortunately the word “repair” is being thrown around by unscrupulous vendors to refer to compiled minerals. "Compiled" means they have found two separate minerals and glued them together to create a more complex specimen. Compiled minerals are more widely considered to be phonies, whereas a repair is an attempt to restore a mineral with a clean break as accurately as possible to what nature created. Repairs also should not be confused with a healed fracture, whereby breaks are naturally fused back together by new mineral growth.

Are repairs phonies?

Repairs are a perfectly accepted and respectable part of the mineral trade—as long as they are disclosed! That’s true of any human alteration. No matter how normal a repair is, it’s hard not to feel a bit bamboozled if you didn’t know about it before you purchased an item.

A lot of mineral collectors prefer not to buy repaired specimens. After all, part of the wonder of it all is that the earth created this! The earth (and some guy with glue) is… somewhat less impressive. A repair can devalue a mineral. All things held equal, a repaired specimen will be worth less than one that is naturally intact. A poorly repaired specimen one will be valued even lower.

There are types of minerals that are routinely repaired, due to breaks caused by the conditions in which they formed and the geologic processes they've been subjected to. When routine, a repair does not devalue the piece. It may even be extremely rare to find complete specimens of certain minerals, such that an intact example is considered especially valuable.

Repairs can be viewed similar to conservation work to preserve museum artifacts. Pinnacle 5 Minerals shares information about the process of repairing and restoring specimens of amazonite and smoky quartz, which routinely need repair work. Clusters of Herkimer diamonds (a form of quartz) are also commonly repaired; the individual crystals have separated in the matrix but can still be pieced back together like a puzzle with seamless fit. Experts recompile a specimen like this to display the impressive original growth form free from matrix.

Again just like selling a car, any repair work should be disclosed! Unfortunately some materials are so commonly altered that vendors do not bother to disclose; it's assumed. Down the line this can lead to well-meaning sellers failing to disclose because they aren’t aware. Other people can be careless because they don’t believe it matters—or worse, they hide it because they think it would hurt a sale.

Repairs in fossils

Repairs are far more commonplace and accepted practice with fossils. Fossils are more likely to have body parts scattered rather than composed in a clearly visible form. With fossils it is also important to display the most scientifically accurate representation of the original life form. As an example, fossil sea urchins like the ones pictured have had their spines reattached. Or someone’s spines anyway.

How to spot a repair

First of all, don’t go finding problems where there aren’t any; repaired minerals aren’t lurking around every corner, and not every dealer is trying to pull one over on you! Fractures are very common in natural material, so don’t jump to the worst conclusions. This isn’t a checklist you should apply to every mineral before buying it. It’s more a list of things that should get your spidey senses tingling. 

Is the specimen a “thing on a thing”?

Sometimes a mineral will grow with another crystal precariously attached. It can be difficult to extract the specimen from the matrix without dislodging the secondary mineral—or it can be easy to knock it off by accident later. A common type of repair is gluing the mineral back into position. 

The "thing on a thing" is certainly one to watch out for with compiled fakes as well. It’s super easy to make a specimen “unique” by gluing a different mineral on it. A common example is the "selenite perched on amethyst" combo commonly sold as a genuine specimen that nine times out of ten will be compiled with small crystals used to hide the glue at the base of the selenite.

I call my “thing on a thing” mineral specimen “the giraffe.” It’s two calcite rhombs on a white stalactite (poss. aragonite?). After looking at it super closely I’m like 98% sure it is natural and has not been repaired, but I also know an expert repair won’t be apparent (if you have bad news, you know where to find my email). Looking into the top rhomb, there is almost a fuzzy white circle radiating inside it as if the crystal grew around the white stalactite, a good clue it’s not a compiled phony.

Where the two materials intersect, there is white crystal growth that extends from the stalactite onto and into the surface of the calcite. There is no visible clean line where crystal growth appears interrupted or offset, as you would expect if the rhomb had popped off.

Check major cracks for glue

Inspect cracks closely for any substance that does not match the color and texture of the specimen. In this aragonite and calcite specimen, when the specimen was pressed back together the excess glue squeezed out of part of the crack:

Minerals are complex so it is possible for a fracture to naturally "heal," meaning it grows back together. Don't mistake something like this for a glued fracture.

Forms that appear dried from a fluid are a dead give-away for glue. This means looking for things like flow or drip marks, or the way glue separates leaving gaps in cracks. Bubbles or impressions left from burst bubbles will be a clear indication of glue. Today's model is an orange stalactitic chalcedony geode from Morocco.

They tried to cover glue lines

This isn’t necessarily someone trying to be sneaky. Visible glue ruins the illusion! A well-done repair will not have visible glue.

People press mud, dirt, clay, or crushed stone into the glue and blend it into the matrix. If you see cracks on one side, and corresponding discolored crumbly lines like this on the matrix on the back, that’s a big red flag your mineral has been repaired.

Compare the calcite in the previous example: you can cover glue lines with faux matrix, but you can’t really cover them with fresh crystal growth (ignoring this type of synthetic, which is far less convincing). That’s why it’s an indicator The Giraffe has not been repaired.

UV reaction

Glue will often fluoresce under a UV light, and this can light up through mud/clay covering on the back. I don’t know if there is a recommended wavelength but I have been able to detect glue using a 365 nm UV flashlight, which seems to be the all-round most useful wavelength with minerals.

A lot of minerals fluoresce, so you’re looking for unusual fluorescence in the suspected area. Is it extra bright? A different color? Sometimes the broken edges of a mineral will fluoresce brighter, in which case it is expected that cracks will similarly fluoresce. Don’t mistake that for glue.

Will you look at that, turns out those miniature mining scenes aren't natural!