Olivine is one of the most abundant minerals on Earth, making up over 50% of the upper mantle. When magma cools, olivine is typically is the first mineral to crystalize. These volcanic rocks are typically located in the upper mantle, which is around 410 km (255 miles) below the surface of the Earth, making it all but inaccessible. The good news however though, is that due to tectonic forces there are areas of the upper mantle and seafloor that have been brought to the surface in a formation known as an ophiolite.
Ophiolites: a section of the Earth’s oceanic crust and upper mantle that has been uplifted and exposed above sea level, usually on top of continental crustal rocks. It is here, within these formations that we find entire layers of olivine in a formation known as dunite.
Dunite is a layer of olivine of the magnesium-rich form of olivine, known as forsterite, which is the same form we use for Project Vesta. Dunite layers are typically greater than 90% pure forsterite olivine. Some of these layers stretch for hundreds of miles and can be tens of miles wide. Olivine is the first mineral to form as magma cools.
As can be seen above in green at the top of the image, dunite is the end-member of a group known as peridotites, which is a generic term used for coarse-grained volcanic (ultramafic) rocks that form from the cooling and crystallization of molten magma (as mentioned above). For weathering or mineral carbonation, any of the peridotites can be used. We prefer olivine due to it being the fastest weathering silicate (see Goldrich Stability Series) with a ratio of up to 1.25 tonnes of CO2 removed for each 1 tonne of olivine weathered.
If you’re doing research on olivine reserves, if you search for olivine you will typically find only limited results. What to look for instead are the ophiolites described above. Ophiolites have an entire layer of olivine as the 90% pure form, dunite. And to further make it complicated to find olivine reserves, on the ophiolite maps, instead of seeing dunite listed, it is typically lumped into the category of peridotites, as described above. When you look at an average ophiolite, olivine and periodite are typically found at the border between layers in the transition from the crust and the mantle, but this can vary depending on the specific formation.
As an example of an assessible ophiolite, in the area from North Carolina to Georgia to, there are at least “25 large forsterite olivine deposits, remarkably sound and free from alteration minerals, occurring in a belt 175 miles long and 15 miles wide“
You may also find olivine bearing rocks in these other types of geologic settings: Ultramfic intrusions (e.g. Norway, Germany), Alpine peridotites emplaced along thrust falts (e.g. Italy, Spain), Rift zones/basalts of mid-ocean ridges (e.g. Iceland), Volcanic xenoliths (e.g. German Eifel and Kaiserstuhl, Iceland).
To understand the truly massive scale and volume of dunite and peridotite layers, see the green color on the map below from a single ophiolite in Oman, known as the Samail Ophiolite that has enough peridotite rocks that the New York Times ran a story a few years back on this specific formation and said that in terms of the potential for mineral carbonation, in theory, “these rocks could store hundreds of years of human emissions of CO2” :
These rocks are being discussed for mineral carbonation, however, this map should help getting across the scale of the vast reserves of CO2 sequestering minerals at or just below the surface, especially of the type that we plan to utilize for our projects.
What we are looking for with Project Vesta, are the places where the top layers of the ophiolite have already weathered away, exposing the peridotite and dunite layers are at or just below the surface. Those are the optimal reserves that we will be targeting for use.
To help you understand the scale of some olivine quarries, here is an example of photos from a massive dunite layer of an exposed ophiolite in Turkey:
As you can see in the above pictures, the quarrying of olivine can be relatively straight forward. If the olivine and dunite layer is near the surface, it can simply be acquired with the use of excavators.
Here are some pictures from the world’s largest active olivine quarry, Gusdal Pit, in Norway. No chemicals are needed to extract the rock, nothing is underground, the process is not mining, it is surface extraction.
Due to current demand for olivine being low relative to the proven reserves, many dunite reserves and ophiolites are currently not being mined. Many areas are not even fully mapped.
The idea is that Project Vesta’s experiments and demonstration projects for olivine spur global demand and that would lead to additional quarries to open as needed. The largest surface mine in the world, Bingham Canyon, has an excavated volume of over 25 km^3, which would equate to 3-4 years of enough olivine to removal the totality of humanity yearly CO2.
Our goal with the entire project is to help protect the restore the planet and so we are well aware of the potential negative impact of surface quarries that is why we plan to turn our old quarries into eco-reserves that have a net benefit. Our model seeks to minimize transport, and so we want to utilize rock sources within 300km of the coast (186 mi), which is the distance from the coast that includes most of the global population and highest density living.
Essentially, in these areas, there are few areas that are not developed and intensively farmed or industrialized. This means there are little to no examples left of the important ecosystem known as “early successional” landscapes. It turns out that if properly restored and left protected, old quarries and mining sites serve as beneficial preserves for arthropods and other animals. It sounds counter-intuitive, and it is, but this is the strategy we plan to employ to make sure we have a net benefit on the ecosystem, aside from our contribution from CO2 removal and deacidification.
“The traditionally negative view of such sites among ecologists is rapidly changing, as it is becoming clear that in industrialized and intensively farmed regions, they offer valuable refuges for rare organisms. The conservation potential of quarry sites has been documented for vascular plants, butterflies, spiders and wild bees. Quarries typically contain periodically disturbed, early successional and highly heterogeneous surfaces, with extreme abiotic conditions and minimum productivity. Similar conditions have become rare in modern landscapes, because humans increase the productivity of land, promoting middle phases of succession over extremes, so that in many regions those species dependent on early successional, sparsely vegetated habitats are among the most threatened. Given that quarrying and open-cast mining will remain an important economic activity, restoration should maximize the biodiversity potential of extraction sites, especially in densely populated regions where such sites represent the last localities that have escaped intensive farming, forestry or building development, apart from scattered nature reserves.”Spontaneous succession in limestone quarries as an effective restoration tool for endangered arthropods and plants
We plan to work with the local communities to no only provide significant jobs in the quarrying process, but also in protecting and restoring the land when the quarry has achieved its initial purpose to a state that was better than when we found it.
We plan to combine the previous process of maintaining early successional land with the process for restoring the landscape using fill material as demonstrated below:
Full restoration of slope:
Some locals may choose alternatives to fill and may desire recreational areas for water park, amphitheaters or other uses of the land. Once any ecological concerns are met, we will leave those decisions up to the local stakeholders and residents near our quarries to determine for themselves what is needed for their community.