Water Sensitive Stones: Crystals and Water Interaction

Many enthusiasts harbor the misconception that water will dissolve their cherished crystals. While there's a kernel of truth to this, it applies to only a select few. Unfortunately, misinformation abounds on this topic across numerous platforms. Here, I aim to shed light on the crystals that warrant caution, accompanied by the stories and reasoning behind their sensitivity to water.

Aragonite

CaCO3

The stability of aragonite crystals varies by region. The binding matrix of the Brown/Orange aragonites from Morocco disintegrates, allowing the individual crystals to fall free. This phenomenon is particularly noticeable with larger clusters exceeding 5 inches. Similarly, numerous Mexican varieties are susceptible to disintegration upon exposure to water.

Desert Rose (Gypsum)

CaSO4 · 2H2O

Any gypsum-based crystal, whether from Mexico, Oklahoma, Algeria, etc. will dissolve upon contact with water, akin to drywall.

The frosted tips on Mexican desert roses aren't a nod to '90s pop culture but rather a result of deliberate torch treatment. When exposed to a powerful flame, such as that from a tiger torch, the crystal tips undergo drying, turning them white. Therefore, if you encounter a desert rose with crushed areas or damage, carefully applying an open flame from a stronger source than a typical Bic lighter can help blend it seamlessly with the rest of the crystal.

Halite

NaCl

Known colloquially as 'Salt Crystals,' Halite crystals universally succumb to water, melting away like the witch from the Wizard of Oz. Whether sourced from California, Ontario, or Poland, etc. they all share this inherent vulnerability.

Hanksite

Na22K(SO4)9(CO3)2Cl

Belonging to the phosphate family despite its salt crystal origins, Hanksite exhibits a striking green hue. However, it's exceptionally prone to water damage. I learned this firsthand when the steam from my shower in an adjacent room began to dissolve the surface of a beautiful specimen I owned.

Even a seemingly innocuous act, like placing it under the moon for cleansing, proved disastrous for a client I sold one to as dew from the morning collected on it, irreversibly altering its appearance. Once water infiltrates Hanksite, there's no salvaging it. I attempted to restore its luster with mineral oil, and was semi successful.

Meteorite

Varied

There are three types of meteorites stony, stony-iron, and iron. It's worth noting that steel is not prone to rusting, while iron is. This becomes significant when dealing with meteorites that consist of 80% or more iron and haven't undergone any metallurgical treatment to prevent rusting – they're likely to oxidize. Preventing rust isn't straightforward; various methods exist, but none are entirely satisfactory. These methods include coating the rock with substances like Vaseline, microcrystalline wax, mineral oil, clear coat, etc., to block oxygen from reaching the surface. Additionally, the location of the meteorite plays a crucial role; for instance, Gibson meteorites are less prone to rust than Campo del Cielo meteorites.

Opal

SiO2 · nH2O

Opals, while resistant to dissolution, can develop 'crazing' or cracks. With a water content of up to 30%, opals are actually bonded to water in their chemical composition- SiO2-H2O. Their stability varies depending on their origin, with Australian opals being the most durable. Ethiopian opals, mined actively since 2008, are the next most common on the market, sourced from diverse mountain regions, resulting in significant variation. Within Ethiopian opals, there are stable, jewelry-grade gemstones, as well as larger, water-saturated specimens (distinct from hydrophane). The latter must be kept submerged in water and cannot be altered through seasoning and curing. Nevada opalized wood is particularly unstable, often disintegrating within hours to days.

Seasoning Opal

Gemstones like Oregon and Mexican fire opal often require seasoning, typically achieved by allowing them to dry out and cure naturally. This process can be deliberate rather than passive. While not scientifically precise, methods such as wrapping the opal in a damp paper towel and placing it in a partially open baggie, then storing it in a dry, dark location like under a bed or in a closet, can aid in acclimating the opal and slowly evaporating the water. However, this doesn't guarantee a fracture-free opal. Rhyolite matrix (host rock) and opal will undergo different rates of expansion and contraction during drying, leading to stress and distortion- thus cracking and crazing the opal.

Once an opal is cured, it shouldn't be submerged again, as reintroducing water can cause cracking due to differential expansion. The seasoning process typically takes a minimum of six months, so when purchasing freshly mined opals, it's important to consider how long they've been out of the ground. Despite initially appearing intact, cracks may develop over the subsequent months or year.

Pyrite

FeS2

Unlike some crystals, Pyrite won't melt in water, but prolonged exposure can lead to rust. Windex proves effective for cleaning Pyrite, swiftly removing dust and fingerprints without fostering rust, as water might. This is thanks to the evaporative agent in Windex that keeps the crystal from staying wet too long.

Selenite

CaSO4 · 2H2O

While various types of selenite exist, Moroccan Selenite, the most prevalent in today's market, isn't susceptible to water—because it's actually Ulexite. However, other varieties, such as those from Mexico, may indeed dissolve when exposed to water. Notably, New Mexico, USA Selenite sheets undergo cleansing in water basins. To effectively clean the New Mexico, USA selenite windows, they must be fully submerged in moving water, which gradually becomes saturated and must then be replaced. If your New Mexico selenite exhibits scratches, immerse it in a creek for two days. This process often results in the scratches disappearing, leaving the crystal looking refreshed and pristine.

Turquoise

CuAl6(PO4)4(OH)8 · 4H2O

While not all natural (unstabilized) varieties of turquoise disintegrate upon contact with water, Mexican 'Chalk' turquoise is particularly prone to rapid deterioration. It's become increasingly rare to encounter turquoise that hasn't undergone stabilization, as many major mining operations now apply this treatment before bringing the turquoise to market as a courtesy and standard practice.

Summary

In summary, crystals sensitive to water often form through evaporative processes, leaving them anhydrous and prone to reabsorption when exposed to moisture. The term to research further here is “evaporite minerals”.

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