Is Lapis Lazuli Rarer Than Diamond? A Geologist‘s Perspective

Hey there! As a geologist with a passion for colored gemstones, I‘m often asked whether lapis lazuli is rarer than a diamond. While the diamond wins on most measures of geological rarity, lapis has its own unique story of formation and scarcity that contributes to its prized status among gem lovers like us. Let‘s take a fascinating dive into the relative rarity of these two stunning gems from the earth!

How Lapis Lazuli Forms

First, a little backstory on lapis. This vivid blue gemstone forms in marble deposits from the mineral lazurite and other coloring agents like sodalite. Lazurite belongs to the sodalite group of minerals and contains sulfur which gives lapis its rich blue hue.

Now marble may be abundant, but the right cocktail of minerals and heat and pressure conditions to create lapis lazuli is exceptionally rare. Most lazurite deposits will never form into gem-quality lapis! Only very specific metamorphic environments allow lazurite, calcite and pyrite to crystallize into lapis together.

These strict geological requirements restrict major lapis deposits to just a few locations like northern Chile and Afghanistan. Many smaller deposits in places like Russia are now depleted. So a tiny fraction of the Earth‘s marble formations contain these perfect conditions to grow gorgeous lapis lazuli!

The Unique Structure of Diamonds

In contrast, diamonds originate much deeper in the Earth‘s mantle from pure carbon. Here, temperatures over 1,650°C and immense pressures of over 45,000 times atmospheric pressure force carbon atoms into rigid diamond cubic structures.

These tough conditions are found in relatively more places below ancient continental plates all over the world. The pure carbon source helps too – making diamond genesis less reliant on a complex mineral mix like lapis.

But still, the recipe for crystallizing loose carbon into diamonds is freakishly rare even in the mantle! Most carbon will instead form into graphite well before it reaches diamond stability conditions.

Relative Abundance

Now to the numbers! Based on crustal abundance, lapis lazuli concentrations average around 0.0021 ppm while diamonds are far rarer at just 0.0001 ppm on average – over 20 times less common.

When it comes to reserves, around 168 million carats of lapis lazuli are known compared to 1.2 billion carats of diamonds. However, lapis reserves are likely underestimated given its artisanal mining.

Looking at production, around 50 tons or 25 million carats of lapis is mined annually, though output is erratic. Diamond production is about 130 million carats per year – over 5 times higher!

Clearly by these measures, diamond is far more plentiful and mines much larger volumes each year. Lapis lazuli is relatively scarce.

Geographic Limitations

A key factor is the restricted locales that produce gem-quality lapis compared to diamonds. Most lapis comes from northern Chile (Andes) and Afghanistan (Badakhshan), with small amounts from Russia, Pakistan, Italy and India.

Diamond deposits are spread across 35 countries across Africa, Canada, Australia, Russia and more. This extensive geography makes diamond more easily accessible. For lapis, just a few unstable, remote regions provide nearly all supply.

Pricing Disparity

Despite being rarer, lapis lazuli is priced below diamond due to supply dynamics:

• Raw lapis can cost as low as $1 per carat for lower quality material
• Fine quality lapis suitable for cutting still averages just $100 to $150 per carat
• Polished diamonds average around $2,500 per carat – many times more!
• But truly top colored lapis can reach over $2,000 per carat

My Conclusion as a Geologist

After analyzing the geology and market patterns, I can conclusively say diamond is still around 10 to 100 times rarer than lapis lazuli by most metrics. The conditions to form either gem are freakishly uncommon, but diamond‘s reliance on extreme heat and pressure gives it the edge for rarity.

Yet lapis has its own claim to rarity due to how few marble deposits collide with the perfect chemistry needed to crystallize lapis minerals. Top lapis grades are harder to source than many colored gems.

So while diamond is the undisputed king when it comes to geological scarcity, lapis lazuli‘s vivid blue dazzle comes from an equally rare convergence of minerals and geology! Both are true wonders of nature.

I hope you enjoyed this dive into the origins and scarcity of two of our most alluring gems. Let me know if you have any other geologic rarity questions!