August’s birthstone is the peridot, which is a gem-quality variety of the mineral olivine. Peridot is known for its distinctive green color, which can range from light yellowish green to dark olive green. The exact shade of green depends on the stone’s chemical composition as well as the natural coloring agents within the crystal structure. While peridot comes in many shades of green, the most prized color is a vivid lime green with a slight yellowish tinge. This bright yellowish-green is sometimes referred to as “peridot” green.
What Causes Peridot’s Green Color?
Peridot gets its green color from the presence of iron in its chemical structure. Specifically, it owes its color to ferrous iron (Fe2+) ions which become trapped inside the crystal lattice during the mineral’s formation. The iron ions absorb certain wavelengths of light and reflect back green. The more iron a peridot contains, the greener the color.
In addition to iron, peridot may also contain trace amounts of nickel and chromium that can intensify the green color. Nickel tends to impart a yellowish tinge while chromium adds a deeper olive tone. The combination of these coloring agents with iron gives peridot its rich, complex green hues.
What are the Different Shades of Peridot Green?
Peridot is found in many different shades of green from light to dark. Here are some of the most common green tones found in peridot gemstones:
- Lime Green – Vivid light green with a slight yellowish tinge. This bright “spring” green is considered the classic peridot shade.
- Green Apple – A bright, yellow-tinged green reminiscent of granny smith apples.
- Chartreuse – A luminous yellow-green named after the French liqueur.
- Forest Green – A deeper, olive-toned green. Still vibrant but with less yellow.
- Asparagus Green – A yellow-green that resembles the color of asparagus.
- Pistachio Green – A lush green with a slight yellow-brown tint.
- Jade Green – A very deep, rich green like the jade gemstone.
- Olive Green – A dark yellowish-green reminiscent of green olives.
- Emerald Green – A bluish-green tone similar to emerald gems. Very rare for peridot.
As you can see, peridot covers the full gamut of green hues from light yellow-greens through deep olive greens. Lime green is the most iconic peridot shade, but other yellowish-greens like chartreuse and pistachio are also commonly seen in peridot jewelry.
What Factors Affect Peridot Color?
Several factors influence the specific green color that a peridot gemstone displays. These include:
- Chemical composition – The precise mixture of iron, nickel, and other trace elements affects the tint. More iron creates a deeper green while nickel imparts a yellowish hue.
- Size of the crystal – Large stones tend to be darker while small ones are lighter.
- Source location – The mineral content of the rocks where peridot forms impacts color. For example, Arizona peridot is known for lime greens while Russian peridot is darker.
- Cut – Well-cut peridot helps maximize the color potential. Poor cuts can make the stone appear too dark or light.
- Treatments – Some peridot is treated to deepen or lighten the color, affecting the exact shade of green.
Understanding how these different factors influence peridot’s color helps explain why stones from the same source can vary in exact shade. In general, the most prized and valuable peridots are those with a vivid lime green color and just a hint of yellow.
How Does Peridot Get its Color?
Peridot gets its distinctive green colors from trace amounts of iron and other elements that become embedded in the crystal structure. Here is a more in-depth look at how peridot forms and receives its color:
- Peridot forms deep underground in magnesium-rich rocks called peridotite.
- As the mineral crystallizes, atoms of iron, nickel, and other elements get trapped in the lattice structure.
- These impurity atoms absorb and reflect certain wavelengths of light.
- Iron specifically absorbs red and blue light while reflecting back green.
- Nickel absorbs some blue and green light, adding a yellowish tinge.
- The combination of these elements produces the various yellowish-greens that peridot displays.
This natural coloring process explains why larger stones are darker – they have had more time to accumulate iron while forming deep underground. Smaller crystals contain less iron and nickel, giving them a lighter green shade.
How Does Peridot Color Compare to Emerald?
Emerald and peridot are both green gemstones but they get their color in slightly different ways leading to some key distinctions:
|Yellowish-greens from iron||Bluish-greens from chromium and/or vanadium|
|Less expensive||Much more expensive and rare|
|Softer, more fragile||Harder and more durable|
|More inclusions||Fewer inclusions when high quality|
While both stones are green, peridot tends to be lighter yellow-green while quality emerald has a more intense bluish-green color. Peridot is also more affordable and commonly found in larger sizes. The colors may overlap at times but generally peridot and emerald have distinguishable shades.
How do Different Lighting Conditions Affect Peridot Color?
The lighting conditions under which peridot is viewed can have a significant impact on how its color is perceived. Here is how different types of light affect its green tones:
- Daylight – Natural sunlight allows peridot to show its most accurate and vivid green tones. This is the optimal light for color evaluation.
- Incandescent bulbs – The yellow/orange glow of incandescent lighting tends to enhance yellow and brown tints while muting greens. Peridot may appear less vivid under this light.
- LED lights – LEDs give off a harsh, cool light that can make peridot appear darker and less vivid. Green hues may look muted.
- Fluorescent lights – Fluorescent lighting has spikes in the blue and yellow spectrum that bring out these tones in peridot at the expense of mid-range greens.
For the most accurate color representation, gemologists evaluate peridot under natural daylight or full-spectrum bulbs designed to replicate sunlight. Incandescent lights add warmth but diminish vibrancy while fluorescent and LED lights alter the stone’s true green tones. Even the time of day impacts color, with noon sunlight showing the most balanced shades.
Does Peridot Only Come in Shades of Green?
While green is by far the most common and iconic color for peridot gems, other hues can sometimes occur. Less commonly, peridot may exhibit:
- Yellow – With very low iron content, peridot can appear yellowish or golden brown. These stones lack adequate green coloring agents.
- Brown – Heavily included peridots may appear very dark, almost blackish-brown. This can happen when iron oxides form within flawed stones.
- Red – Trace elements like manganese can give some rare peridots a reddish or purplish partial tint. This is highly unusual.
- Blue – Similarly, some chromium-containing peridots have a bluish secondary hue along with green.
However, these non-green peridots are uncommon. The vast majority of peridot gemstones exhibit some shade of yellowish-green reflective of their iron-rich composition. Stones lacking discernible green are typically not considered “true” peridot gems.
How Durable are Peridot Colors?
While peridot’s colors are natural and do not require treatment, they can be prone to fading if not properly cared for. Here are some tips to keep peridot’s green tones vibrant:
- Avoid prolonged sun exposure which can bleach and fade peridot over time.
- Clean peridot with mild soap, water, and a soft brush; avoid harsh chemical cleaners and ultrasonic cleaning.
- When storing, wrap peridot in soft cloths or place in fabric-lined boxes to prevent scratching.
- Remove peridot jewelry before physical activities like sports, swimming, or heavy yardwork where roughness or chemicals can damage the stone.
- Consider having fragile peridot set in protective styles like bezels that do not expose edge areas.
With some basic precautions, peridot can maintain its lovely green hues for many years of wear. Taking steps to prevent scratching, fracturing, and harsh cleaning preserves the crystalline structure that gives this stone its color.
August’s glittering birthstone peridot comes in a veritable rainbow of yellowish-green hues from light chartreuse to deep olive. Its signature color results from trace iron impurities in an otherwise colorless crystalline structure. Lime green with a hint of yellow is the most prized peridot tone but natural variations in size, chemistry, and source location lead to an array of greenish shades. While a fragile stone, peridot’s lovely colors can stay vibrant for many years with proper care and protection from damage. Whether light or deep-toned, the many greens of peridot fittingly represent the colors of late summer.