Prehnite is a beautiful and unique mineral with an unusual glassy texture which occurs in an array of pale green hues. While it is not the most well-known gemstone, it does make a wonderful choice for jewelry, and it looks great in any mineral display case.
Read on to find out more about this striking gem!
TABLE OF CONTENTS
What is Prehnite?
Prehnite is classified as an inosilicate of calcium and aluminium, and has the chemical formula Ca2Al(AlSi3O10)(OH)2. The orthorhombic crystals typically look bulbous.
Prehnite is not classified as a zeolite, but it is frequently found together with calcite, datolite, laumontite, stilbite, and so on.
Prehnite Properties and Color
The luster may range from vitreous to pearly, and often has a look like frosted glass. The gem is very brittle and has an uneven fracture with a hardness of 6-6.5. While prehnite is occasionally transparent, it is typically translucent.
In terms of color, there is actually quite a bit of variation in prehnite. Prehnite typically occurs in green, but you can also find specimens which are blue, colorless, pink, or white. Prehnite may even come in orange, as evidenced by the discovery of such a rare specimen in the Kalahari Manganese Fields in South Africa in 2000.
What shade of green does prehnite come in? One of the fascinating things about prehnite is that it actually may be found in a very wide spectrum of greens. Many green minerals are only yellowish-greens or bluish-greens, but prehnite may actually fall anywhere within that color spectrum. Its hue may be warm or cool. In most cases, however, it is fairly pale and milky. Sometimes the stone features dark inclusions.
There are no noteworthy industrial uses for prehnite. It is mostly used in gemstone jewelry. It may also be carved into figurines.
Prehnite Buying Guide
When you are shopping for prehnite, there are a number of factors which you should take into account:
- Size: Carat is not necessarily going to be a huge arbiter of price, but it will certainly have some impact. Naturally you will pay more for a larger piece than you would for an otherwise comparable smaller stone.
- Color: Which color of prehnite is best? That is totally up to you! You should purchase prehnite based on your preference (or the preference of your recipient). Some people may prefer the more yellow tone, while others may prefer the more bluish tone. Others may look for a truer green. Usually the more saturated stones will be more coveted—this is pretty much par the course with most colored gemstones. But the milky specimens can be quite desirable too. Keep in mind that if you are looking to buy one of the rarer colors, you will probably pay a lot more for it.
- Cut: Prehnite gemstones are often sold tumbled and polished, but they are actually faceted surprisingly often. If you are buying one of the more transparent specimens, the particular cut of the stone may help to bring out its clarity. In most cases, prehnite will be murky to look at, so you should pick the cut of the stone based on other aesthetic considerations.
- Transparency: The vast majority of prehnite specimens are milky in appearance, not fully transparent. As I mentioned earlier, some even have inclusions. Because these translucent and included specimens comprise the vast majority, they are still considered desirable. But if you can find one of the rarer transparent pieces which actually offer some glassy clarity, you can expect a higher price tag.
So while there are some factors influencing price, in general you should purchase prehnite based on your personal taste. You may also want to look into buying raw specimens. The crystals are quite fascinating to look at, and there are some really cool formations which would look awesome in any collection of minerals.
Prehnite is not expensive. You can get a long strand of prehnite beads wholesale for $15 or less. You can get a number of prehnite cabochons for the same price.
So the major cost with prehnite jewelry is not the gemstone itself, but rather the setting and any other gems which are used as part of the design. The craftsmanship of the piece may also raise the price.
You will find all kinds of prehnite jewelry for sale. This includes earrings, rings, pendants, necklaces, bracelets, and brooches. Because prehnite gemstones can be relatively large, they are perfect for larger jewelry items—but small prehnite gems can also be mesmerizing to look at.
You will even find prehnite engagement rings, although they are not very common.
Prehnite Engagement Rings
The vast majority of prehnite engagement rings are handcrafted. You will rarely find a prehnite engagement ring produced by a major jewelry brand. Major brands typically stick with diamonds and other precious gemstones.
There is quite a bit of variety with the prehnite engagement rings you will find for sale. You will discover that both gold and sterling silver bands are popular (as well as white gold).
Some rings use faceted prehnite gems, but many actually feature rounded cabochons instead. These really capture the milky depths of prehnite in a captivating way.
It is common for prehnite engagement rings to be encrusted in diamond accent gems. This of course increases their financial value.
- Prehnite is a beautiful and unusual gemstone for an engagement ring. Almost everyone has a diamond engagement ring, so a prehnite ring will be a natural conversation-starter.
- Because prehnite is available in many different shades of green, it is possible to find a ring which may suit any skin tone. If you are looking for something which is neutral enough to match any wardrobe, you can shop for clear or colorless prehnite, or go with a very pale milky green.
- Because prehnite does not cost that much on its own, you can spend more money on the band.
- Because prehnite is brittle and only ranks at 6-6.5 on the Mohs scale of hardness, it may easily fracture if it is banged against a surface or dropped. On the bright side, if you should need to replace it, it will be relatively inexpensive and easy to do.
- Prehnite usually has no significant financial value, unless you have a piece in a rare color. For that reason, it does not necessarily make the best investment; you can pass it down as an heirloom, but its value will principally be sentimental in nature, not financial.
- Prehnite is nontraditional. Many recipients are only open to a diamond engagement ring. The only way for you to be sure is to ask your partner. Even if you feel pretty sure she would like prehnite, you really do not want to take any chances here. When and how you propose should generally be a surprise. The type of ring and gemstone should not be.
How to Clean and Store Prehnite
How you clean prehnite depends largely on whether you are trying to clean a raw or polished/faceted specimen. If you are cleaning a faceted or polished piece (as in jewelry), you should follow the usual procedure of scrubbing gently with mild detergent and an old, soft toothbrush. You can then mop the piece dry or you can let it air-dry. Just do not use any harsh chemicals, and make sure you get all the soapy residue off (rinse thoroughly). When polishing the setting, stick with a jeweler’s polishing cloth.
What about raw prehnite? That can be quite a bit more challenging. A high-pressure water jet can do a good job, but it can be very hard to perfectly preserve and polish the luster on the surface of the crystals. You can read in-depth about this challenge here. One thing which is very important to know is that you should never use acid to clean prehnite. Doing so will actually destroy that luster that you are trying to bring out.
Because prehnite is softer than many other gemstones and metals, you will want to take extra care when you are storing it. You should keep it in its own separate container. This can be a lined box or a soft pouch. Prehnite should be stored in a cool, dark place, just like the rest of your gemstones.
Note that the longer prehnite is exposed to open air, the more its color will fade gradually over time. Sadly there is not much you can do about that; it is simply what happens to all prehnite. This is why most prehnite specimens have such a pale color.
As with storing prehnite, wearing prehnite requires a little extra care. Remember, this stone can easily be scratched or fragmented if you bang it into a wall or countertop or drop it on the floor. So do not wear it if you are going to be physically active.
Also keep it away from household chemicals, so no wearing it while you are cleaning house. Mind that you do not expose it to cosmetic chemicals either.
Beautiful botryoidal prehnite specimen by Treasure Mountain Mining (not affiliated).
We do not know a whole lot about the history of prehnite because the mineral wasn’t even identified until the 18th century. It was first found and labeled in the year 1788 in the Karoo dolerites of Cradock, Eastern Cape Province, South Africa.
The name is derived from that of Colonel Hendrik Von Prehn, who commanded the military of a Dutch colony located at the Cape of Good Hope between 1768 and 1780. There is a curious amount of uncertainty surrounding Von Prehn. For example, no one is positive when or how the “Von” in his name was conferred upon him. Supposedly it was out of recognition for his actions during the Seven Year’s War, but there are no records which prove that.
It is known that Von Prehn was a mineral collector, and that it was he who brought the first recognized specimen of prehnite to Europe. But no one seems to know how Von Prehn stumbled upon the mineral in the first place.
While prehnite may have been in use before the 18th century, there is no solid documentation on that use.
Because of its green hue, prehnite is readily associated with the heart chakra. This makes it an excellent stone for emotional grounding, balancing and stability. It is a good stone for promoting self love as well as understanding in relationships. Like some other green stones (such as peridot), it is also linked to prophecy in metaphysical circles.
Even though prehnite is a fairly unique gemstone, there are a few other stones which might be confused with it from time to time.
- Smithsonite: This is a calcite group mineral which may form globular green clusters which could easily be mistaken for prehnite. How can you tell the two apart? Smithsonite weighs more than prehnite and also gives off bubbles in hydrochloric acid.
- Peridot: Peridot is the name for gem-quality olivine. It is one of the most common gems to make this list. In terms of color, it can vary, but usually it is green, greenish-brown, or yellowish-green. As you might guess, its most common and distinctive hue is olive. It has a glassy luster which combined with its color makes it easy to mistake for prehnite. On top of that, even its hardness is similar, 6.5-7.
- Wavellite: Wavellite is one of the most striking minerals you will ever see. It often forms in a very distinctive radiating “wheel” shape. These wheel shapes are actually cross-sections of spherulitic ball structures. When the ball structures are complete, you cannot see the radial patterns inside. Instead, you end up with globules which once again can resemble prehnite, especially since they tend to feature a similar pale green color. Wavellite however is found in different environments than prehnite. So if you know the history of a gem, you may be able to determine whether it is wavellite or prehnite.
- Hemimorphite: This mineral can also appear very similar to prehnite when it occurs in a green hue. You can distinguish between the two because prehnite is both harder and lighter in weight.
- Green chalcedony: This cryptocrystalline quartz is regularly mistaken for numerous other gemstones, in part because it is so common and in part because its appearance can have so many striking variations. Green chalcedony is often milky and translucent in appearance and may sometimes have a similar washed-out color to prehnite. Many specimens however are a much deeper, bolder, truer green. The luster is waxy and the hardness is 6-7.
- Green beryl: Green beryl is actually emerald. While you might think of emerald as a vivid, deep green color, some specimens are actually quite a bit paler, and share the same glassy luster as prehnite. They are usually clearer, and they are significantly harder, 7.5-8 on the Mohs scale. If you see a green beryl crystal in its raw form, you will notice it has a very distinctive hexagonal shape which you really can’t mistake for anything else.
- Jade: Jade can actually be either of two different types of minerals, neither of which are related to prehnite. Jade’s appearance can vary wildly, but some specimens may resemble prehnite. What is the easiest way to recognize true jade? Hold it up to a light and look through it. If you see a lot of fibrous little inclusions, you are probably looking at jade, not prehnite or another similar-looking gemstone. Hardness measures between 6-7.
- Green fluorite: This is the mineral form of calcium fluoride. Curiously enough, fluorite itself is actually colorless, but it can contain numerous different trace elements which may lend it a myriad hues. The green specimens can look a bit like prehnite because of their pale colors, but they may include other color zones as well (not always). You will also notice inclusions in many specimens which give it a very different look than prehnite. Prehnite may be murky-looking, but it usually doesn’t feature inclusions like these. Prehnite inclusions (when present) are usually much darker and sharper in appearance.
So now you know all about prehnite! Prehnite may lack the clarity and sparkle of a diamond, but it makes up for that with its lovely milky green color and translucency. It captures the light beautifully, especially when it is tumbled and polished into cabochons.
In its raw form, it is also particularly breathtaking. Prehnite makes a wonderful inclusion in your gemstone collection!