Lepidocrocite vs Lepidolite: What Are They, And What's The Difference?

Lepidocrocite and Lepidolite are both minerals that share many similarities, such as their almost identical, confusingly similar, names, and the simple fact that they are both minerals.

But, I have also outlined below, there are many differences and distinctions between the two.

Lepidocrocite vs Lepidolite (Explained)

Lepidocrocite Facts

Lepidocrocite is a polymorph of goethite (they are often associated because of their similar physical properties).

It is also sometimes referred to as esmeraldite or hydrohematite, and is an iron oxide-hydroxide mineral (the result of the oxidation of iron by way of water).

Lepidocrocite has what is called an orthorhombic crystal structure, which means its lattices are a direct result of stretching the cubic lattice across two orthogonal pairs by two different factors, which in turn results in a rectangular prism formed by a rectangular base and height.

Also, orthorhombic structures have three bases that intersect at 90° angles, which allows for their three lattice vectors to remain orthogonal.

Lepidocrocite maintains a hardness of 5 on the Mohs scale, a gravity of 4, a submetallic luster with a yellow to brown streak.

It has a color range between red to reddish-brown, gray to white in reflected light, and forms whenever iron-containing substances fully rust when submerged in water.

Because of Lepidocrocite’s formation and recognition of this reaction to water, it is also commonly found in iron ore deposits and through the weathering of primary iron substances.

Lepidocrocite is also frequently observed and found within the rust scale inside aged steel water pipes and inside (mostly in the metallic lining) of water tanks.

The structure of lepidocrocite is like the boehmite structure in that they are both orthorhombic crystal structures that are composed of octahedral double layers of edge-shared octahedra but differing mostly by the surface oxygens layers containing hydroxyls and the double layers that are aligned along the b-axis bound together by hydrogen bonds found in bauxite and consists of layered iron oxide octahedra that are bonded together by hydroxide layers.

Because of this weak bond layering, it is a very scale mineral.

Its chemical formula is γ-FeO (OH), its formulaic mass is measured at 88.85 g/mol and has flattened scales that are aggregated into plumose groups and rosettes classified as massive and range from bladed to fibrous to micaceous.

It has perfect cleavage, transparent diaphaneity, and biaxial optical properties.

Lepidolite Facts

Lepidolite is the name given to an ultra-rare lithium-rich mica mineral.

It is frequently thought of as the most common and abundant of lithium-bearing minerals. It serves as a minor ore or what is referred to as a secondary source of lithium metal.

It produces two main products, rubidium and cesium, which are both defined as monovalent alkaline metals and are among those which present the highest number of protons and atomic weight.

It is also associated with many lithium-bearing minerals like spodumene in pegmatite formations and can also be found in high-temperature quartz veins, greisens, and granites.

More minerals that are frequently associated with lepidolite are amblygonite, beryl, cassiterite, columbite, feldspar, spodumene, tourmaline, topaz, and quartz.

When combined with quartz, lepidolite is sometimes used as a minor or ornamental gemstone.

A lot of the coloring of the mineral comes from its small pink and red aventurine flakes.

Lepidolite’s coloring can also be understood as being a lilac-gray to rose-color but is most often observed as pink, red, or purple stone, but also gray and, rarely, yellow, and colorless.

The trace amounts of manganese inside are thought to be the cause of its pink, purple, and red coloring.

Lepidolite has the chemical formula of K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2.

It is a phyllosilicate mineral (also called sheet silicates.

It is a group of minerals containing micas, chlorite, serpentine, talc, and clay, which is of importance because clay minerals are one of the primary products of chemical weathering and one of the more abundant constituents of sedimentary rocks), and a member of the polylithionite-trilithionite series, any mineral between Polylithionite and Trilithionite has not yet been specially categorized and defined.

Lepidolite is a rare member of a three-part series of minerals that consist of polylithionite, lepidolite, and trilithionite.

These minerals are often grouped together because they share many properties, and all contain varying ratios of lithium to aluminum present in their chemical formulas.

Lepidolite is found throughout the world, but perhaps most notably and abundantly in the Ural Mountains of Brazil, Bernic Lake, California, Canada, the Tanco Mines, Manitoba, Madagascar, and even in some parts of Russia.

Lepidolite is a member of the phyllosilicate family, and is classified as being a part of the monoclinic crystal system, having tabular to prismatic pseudohexagonal crystal formations with scaly aggregates and massive crystal-forming habits, perfect cleavage with uneven fractures, measuring between a 2.5 and 3 on the Mohs hardness scale.

It has a vitreous to sometimes pearly luster with white streaks and can appear transparent to translucent with a specific gravity between 2.8 and 2.9.

Lepidocrocite and Lepidolite (Compared)

While both Lepidocrocite and Lepidolite are both minerals and share uncannily similar-sounding names, these two minerals are quite different.

Aside from their chemical formulas and structures, one of the most glaring differences between the two is their appearances.

Lepidolite has a vitreous or pearly luster, comes in pink, light purple, purple, rose to red, violet to gray, yellowish, white, and colorless, with white streaks and appears transparent to translucent.

Lepidocrocite has a submetallic luster, comes in more of a ruby reddish to reddish-brown (so a bit darker reds than lepidolite), is red-orange in transmitted light, and can change colors to appear gray to white in reflected light, with dull orange streaks and only appear transparent with a solid gravity of 4.

Lepidocrocite is a much darker mineral in color, and a heavy, or denser, material.

Another noteworthy difference between the two almost indecipherably named minerals is their measures on the Mohs hardness scale.

This measuring is particularly important to note in the classification of these two minerals, and the general distinctions between the two, because this reading greatly determines how a mineral feels not only in direct comparison with another but to the touch of the observer.

This measurement only confirms the above acknowledgment that lepidocrocite, measured as a solid 5 on the Mohs hardness scale, is a much denser solid mineral than lepidolite, which measures between 2.5 and 3 on the scale.

So, while the names may trip you up and lead one to believe they just misspelled, or misidentified, one mineral for the other, these minerals are drastically different in many ways.