Diamonds are prized for their rarity, but supply and demand still enter into the equation. Diamond mining companies must not only produce a certain quantity of stones, but a quantity of stones at a certain base level of quality, in order to keep up with the market.

What happens when a company starts to struggle? Anjin Investments is finding out, as their operations in the Merange gem fields of Zimbabwe have been struggling as of late to produce enough stones at a high enough grade to keep the mining effort afloat.

Despite having recently invested nearly $400 million into the operation, officials say they are basically in “survival mode”, citing dwindling resources and lower revenues.

But other mines seem to be in fine running form. The Letseng Mine in Lesotho, for example, recently made headlines in the diamond world by producing two impressive diamonds, weighing 162.06 carats and 161.74 carats.

Diamond prices are determined by the purpose for which the stone is intended. Only about 20% of the diamonds mined from the earth are considered “gem quality” and suitable for jewelry, and these diamonds will fetch a naturally higher price per stone. Industrial-use diamonds, on the other hand, are often bought in bulk at lower prices.

Are we likely to run out of diamonds some day? It’s not so much a matter of knowing where they are — it’s a matter of reaching them. All of the diamonds we retrieve from mines were actually relocated by volcanic eruptions long ago. The stones themselves form only within a narrow range of temperature and pressure located about 90 miles below the surface of the Earth. For comparison, the deepest mine dug by humans was a gold mine in South Africa, reaching 3,581 meters — or only two miles.