Lepidolite and amethyst have a lot of superficial similarities, but at the end of the day they’re entirely separate minerals. That said, in some forms they can be hard for a new rockhound to tell apart, so it can pay off to actually learn the differences between the two.
So, read on for our comparison of lepidoliute versus amethyst, and we’ll teach you how to tell the difference!
What is Lepidolite?
Lepidolite is a lithium rich mica mineral, which ranges from a grey-lavender to purple to rose colored depending on the impurities contained within itself. The often seen shades of purple and red are actually from trace amounts of manganese contained within the mineral.
Like all micas, ledpidolite is stacked in thin layers. These are bound together weakly by potassium ions. In between these bonds is a TOT structure, which consists of tetrahedral layers encasing an octagonal layer on a molecular level.
Lepidolite generally occurs in granitic pegmatites, but it’s also found in some other high temperature granites, as well as quartz veins. It’s the most common lithium-bearing mineral, but it’s only considered a secondary source of the valuable mineral. It’s instead used as the primary ore for the extraction of the rare earth metal rubidium
Rubidium is primarily used in high-tech applications such as atomic clocks, photo cells, and imaging brain tumors due to the bodies tendency to accumulate rubidium in them.
Lepidolite itself is a very soft mineral, being only 2.5-3.0 on the Moh’s scale. It’s still a favorite for collectors, however, due to the great coloration the stone often holds. In the USA it’s found in a few places, primarily in Montana and California.
What is Amethyst?
Amethyst is a mineral in the quartz family. Specifically, amethyst is comprised of macrocrystalline silica, with iron replacing some of the silicon atoms in the lattice of the crystal. This gives it the purple coloration that so many people find attractive.
At higher heats during formation, this same crystal lattice actually forms the much rarer citrine. Differential heating can result in a combination of the two color zones, generally called ametrine. It also forms the rarer variant prasiolite in an extremely small band of temperatures between amethyst and citrine.
Amethyst is generally used as a gemstone or just collected. It’s not a commercially viable source of any particular elements. It was quite rare early in European history, which led to it being considered one of the classic precious stones. The discovery of large deposits in the Americas, however, led to it being “downgraded” to just a semiprecious stone.
Amethyst is universally purple, this color is the defining feature of the crystals. That said, they vary from very light lavender to a deep, richly saturated purple. The latter are much more rare, and are worth hundreds of times more per carat than those with less coloration.
Amethyst is collected in all the forms that you find quartz in, from crystal points to clusters, to tumbled stones and faceted gems. Amethyst is quite hard, running a 7.0 on the Moh’s scale and keeping in line with all other quartz varieties.
Amethyst is widely spread in the Americas, but the largest deposits are in the basalt fields of Brazil.
How Are Lepidolite and Amethyst Similar?
Both of these minerals have purple coloration. They’re both silicate minerals as well, although the complex structure of lepidolite is very different from the basic hexagonal silica form that amethyst takes.
On occasion, lepidolite also forms a rather anhedral hexagonal system, but its distinct from amethyst to those who are paying attention. It actually forms monoclinic crystals, despite this superficial similarity.
Overall the two aren’t remotely related, apart from the fact that tumbles of the materials can often bear the same shades of lavender and purple.
How Are Lepidolite and Amethyst Different?
The most easily identified difference of these minerals is simple: lepidolite is orders of magnitude softer. If you’re unsure, scratching at the stone with a piece of steel will quickly let you know which you have. Lepidolite will scratch, while amethyst’s surface will remain impervious to it.
Structurally, they’re not remotely related. Lepidolite is a mica mineral, which are known for their pleasing crystal shape. Lepidolite, on the other hand, is found as scattered particles, flaky layers, or aggregate crystals.
While amethyst is transparent in most cases, lepdiolite ranges from translucent to opaque depending on the form it takes and the impurities inside of it.
Lepidolite also has a wider range of colors than you’ll find in amethyst. Some of it is grey, and some of it is rose, although a light purple seems to be the most common color found. Amethyst, as stated above, occurs only as a purple mineral.
Both are used in jewelry, but gem-grade lepidolite is vanishingly rare. Those found intermixed with quartz can be cut into striking cabochons, but faceted stones are only of interest to collectors. They’re simply impractical to wear thanks to the softness of the stone.
One thing to keep in mind if you own jewelrey with lepidolite in it: the stone shouldn’t be worn in the shower. It’s fairly reactive and it can damage the stone with repeated exposure to moisture. If your shower is damaging your amethyst, however, then you have much bigger problems. Very few chemicals affect silica at all, and those that do are things like hydrofluoric acid.
Lepidolite vs Amethyst FAQ
Q: Does lepidolite sparkle?
A: Like other mica minerals, lepidolite will often have a sparkly surface. This due to the varying surface planes of the rock, causing them to reflect light at different angles relative to the viewer. Ledpidolite shares this property when found as an aggregate.
Q: Can you tumble lepidolite?
A: Yes, but you should take care what other stones you have in there with it. Dense, hard stones like agate or jasper will simply crumble it. While it’s best to tumble it by itself, calcite and fluorite are two examples of minerals that shouldn’t cause any extra damage.
Q: What minerals are associated with lepidolite?
A: Quartz, tourmaline, and feldspar are the most common. There are many others, including lithium rich minerals like spodumene and common finds in pegmatites such as beryl and topaz. Due to the granitic pegmatites in which lepidolite is commonly found, it’s more of a feature of lithium-rich areas, rather than having a close association due to common formation actions.
Q: How much is lepidolite worth?
A: Lepidolite is fairly cheap in most cases. It’ll generally run you about $.50 per gram of material when rough. Cabachons are generally made from specific material containing harder minerals like quartz, however, and will generally be on the upper end of the middle range for cabochons despite their softness.
Q: Is amethyst ever treated?
A: Yes… and no. Heat treatment of amethyst is surprisingly common, but the results generally aren’t called amethyst. Differential treatment results in ametrine, while heating can result in prasiolite or citrine. Most citrine on the market is actually heat treated amethyst, and the matter is hotly debated by some. The only difference between these minerals is the heat at which they form, so the matter is largely academic.
Q: How much is amethyst worth?
A: It varies widely. Common, clear stones with little color may only be a few cents per carat. Deeply colored stones are generally more costly. Amethyst can have undertones of either red or blue, and the most highly valued are Siberian amethyst which have a red flash when viewed in the right light in addition to their deep purple color. Mineral samples are generally priced based on their size.
Q: Is ametrine a natural variant of amethyst?
A: Yes, but most of the material you see is altered amethyst. The only significant occurrence of ametrine occurs in Bolivia, so knowing the provenance of the stone is extremely important if you have problems with heat treated stones. It’s sometimes sold under the name bolivianite as well.
