For rockhounds with a decided affinity for the color green, tourmaline and epidote stand out among the pack.
Due to their similar colorings, these two rocks can confuse even seasoned rockhounds.
However, as we will review throughout this article, these stones have just enough differences for amateurs and professionals alike to distinguish them with the naked eye and careful attention to little details.
Epidote vs Tourmaline: Explained
What Is Tourmaline?
The name “tourmaline” refers to a large classification of minerals that frequently present as an accessory to igneous or metamorphic rocks.
This mineral’s coloring ranges from blue, green, yellow, pink, red, orange, purple, brown, and colorless.
The most common color for tourmaline is black, but it does present in a wide range of other colors.
This makes it popular around the world for it’s versatile hues.
In terms of hardness on the Mohs scale, tourmaline tends to range from 7 to 7.5, which makes it tough as steel nails (approximately).
When it comes to specific gravity, tourmaline registers between 2.8 and 3.3–this fluctuates depending on changes in the stone’s chemical composition.
Tourmaline’s chemical composition resembles something like this: Ca,Na,K,(vacancy).
That vacancy can be filled with a variety of minerals including (Li,Mg,Fe+2,Fe+3,Mn+2,Al,Cr+3,V+3)3, (Mg,Al,Fe+3,V+3,Cr+3)6 ((Si,Al,B)6O18) (BO3)3, and (OH,O)3 (OH,F,O).
In plain terms, the chemical composition of tourmaline makes it a borate silicate mineral that compounds aluminum, iron, magnesium, sodium, lithium, or potassium.
For streaks, rockhounds should look for a white streak when it’s softer than the streak plate and colorless when it is harder than the streak plate.
Tourmaline gives off a vitreous luster.
A tourmaline’s diaphaneity or level of transparency ranges from transparent to translucent to borderline opacity depending on the specimen.
The stone’s cleavage remains indistinct and it adopts a hexagonal crystal system when forming crystals.
Both professional and amateur rockhounds can identify a potential tourmaline specimen by an absence of visible cleavage, its unique prismatic crystals that possess rounded triangular cross-sections that are frequently striated with white or colorless streaks, vibrant colors, and pleochroism.
Tourmaline is mostly used for decorative and fashion purposes.
Some individuals who are into crystal healing use this stone to ward off perceived negative energy.
Serious rockhounds mostly appreciate tourmaline for the beautiful pop of color it can add to their collection and the sense of pride that comes with successfully identifying tourmaline.
After all, this stone can resemble other types of minerals such as serpentine and epidote.
Where Can Rockhounds Find Tourmaline?
Tourmaline tends to be presented as igneous and metamorphic rocks as an accessory mineral.
During the hydrothermal activity, tourmaline also forms in cavities and caves as large crystal specimens.
Although tourmaline is a pretty crystal, it is also incredibly durable and hard.
This allows it to survive tumbling down streams and beaches along with enduring as small grains in sediment and sedimentary rocks.
It can also be found around metamorphic rocks, including pegmatites.
These rocks sometimes contain crystals such as quartz and mica as well.
Around the world, Brazil has been the major source of tourmaline internationally for almost five centuries.
In the United States, tourmaline can be found as far east as Maine and as far west as California and Colorado.
Regardless of what coast rockhounds hail from, they are sure to be close to tourmaline specimens just waiting to be discovered.
What Is Epidote?
Epidote runs the color wheel from greenish to yellowish to black-tinted stone with a vitreous to resinous luster and colorless streak.
Some call it “Pistacite” for its pistachio-like coloring.
On a chemical level, epidote is composed of the formula oCa2(Al,Fe)2(SiO4)3(OH) and a basic calcium aluminum iron silicate composition.
Sometimes this silicate mineral presents a cleavage following an impeccable pattern in one direction–other times the pattern is uneven.
On the Moh scale, this stone ranges between a 6 to 7 hardness.
Epidote’s specific gravity runs between 3.3 and 3.5.
These characteristics, when paired with its signature hues, differentiate epidote for amateur and professional rock lovers alike.
Many fine gem collections around the world feature this light green semi-precious stone.
Voracious gem and mineral enthusiasts treasure this earthy green stone. It often finds its way into jewelry and displays.
Where Can Rockhounds Find Epidote?
In the United States, Epidote occupies North Carolina, where it was initially identified.
It also exists in Virginia and in Alaska. Epidote also lives in Nevada, Vermont, and New Jersey.
From the north to the south, east to west, epidote is easy to find.
Internationally, epidote abounds from the European Alps to Pakistanian clefts.
France, North Africa, and Brazil have also boasted wonderful occurrences of epidote through rock hounding history.
This mineral is fairly common, but its prized color dazzles rockhounds regardless.
Rockhounds can locate this mineral as a secondary element in metamorphic rocks such as in limestone as well as through contact zones between igneous and calcareous sedimentary rocks.
Sometimes, epidote even occurs within other gems such as quartz or calcite.
This rock frequently gets mistaken for tourmaline and vesuvianite.
It also gets confused for tourmaline, which we will discuss in the next point.
Why Do Some People Confuse Epidote and Tourmaline?
Often, epidote and tourmaline get confused due to their similarities in coloring and their slightly metallic qualities as minerals.
As an example, both stones have white or colorless streaks and sometimes exhibit green, black, or light brown casts.
Also, both stones are found in metamorphic rocks.
For those who are into rock collecting for the aesthetics, these stones have similar decorative purposes and prevalence.
These qualities can make the two specimens hard to differentiate.
How Can Rockhounds Tell Epidote and Tourmaline Apart?
In spite of their similar colorings, epidote and tourmaline possess different color patterns.
Tourmaline frequently features color zoning whereas epidote does not.
Tourmaline also tends to be presented as a sage green while epidote tends to favor the olive tones of green.
Their hardness on the Moh scale is pretty close, but tourmaline tends to be slightly harder. epidote also shows a higher specific gravity on average than its tourmaline counterparts.
In crystal form, epidote tends to take on long, slender connected prismatic shapes.
Alternatively, tourmaline tends to connect in hexagonal shaped prisms.
Especially in the case of green epidote and green tourmaline, they may be challenging to distinguish at first glance.
However, when in doubt, a skilled mineralogist from a local gem and mineral club or rock-hounding organization can steer stumped rockhounds in the right direction.
In conclusion, epidote is a type of silicate mineral that populates almost every corner of the globe. It comes in a wide range of colors, most popularly green, and is highly desirable to gem and mineral collectors and jewelers, but not very useful outside of its beauty.
Tourmaline is a category of borate silicate minerals that resembles epidote due to its greenish tint.
However, tourmaline’s crystal formation, hardness, and coloring are different than epidote in most cases.
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