So in a previous blog, I discussed with you how diamonds form, where they’re found, and how they’re brought up to the surface. I also discussed why I believe we have no diamond deposits here in the Philippines so for this blog, I would like to discuss what are the typical gemstones we have here given the age of our landmass (the Philippines is a mere “child” of 50,000 years old).
To start off the discussion, I’ll need to discuss with you the various rock cycles.
Igneous Rock Formation
These are rocks that started out in a molten or semi-molten state as the earth was forming and eventually became solid when the earth, as we know it, started cooling down. Two of the most widespread igneous rocks are granites (rich in elements like silicon, oxygen, and aluminum) and basalts (rich in iron and magnesium). As the earth cools, the combination of heat and pressure formed other types of rocks.
Metamorphic Rock Formation
These are rocks that got altered due to heat and pressure transforming old rocks and minerals to new ones. Marble is an example of this and the exposure to heat and pressure underground may alter other minerals found within the marble that can contribute to the formation of corundum crystals!
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Sedimentary Rock Formation
These rocks are produced from weathered products of existing rocks caused by atmospheric changes like rains, earthquakes, and wind to name a few. The sediments brought about by these weathering processes eventually accumulate in thick layers over time eventually hardening into rocks as pressure from above compacts these sediments into hardened layers. These sedimentary rocks form closer to the surface and are quite plentiful.
We now have a general understanding of the various rock formations and how they came to be. We also know that the Philippines is quite young in terms of age so logic tells us that most of the gemstones we have in our country are those which originate from sedimentary rocks.
What are Gems from Sedimentary Rocks
Some notable gems from sedimentary rocks are opals, malachites, turquoise, and quartz.
The finest opals in the world are mined from eastern and central Australia where there’s limited seasonal rainfall. Opals tend to form in arid weather conditions since oral deposits form through evaporation. Water percolates down through sediments or volcanic rocks rich in silica and carry the silica down to the water during the rainy season, filling up the cracks and voids in the rock and when the water evaporates during the dry season, the silica is deposited as submicroscopic spheres in the open spaces in the rock eventually providing the play-of-color optical effect in opals.
In the Philippines, we have a lot of malachites and quartz.
Malachite forms when acidic and copper-rich solutions react with limestones. Quartz is made of the two most abundant chemical elements on Earth: oxygen and silicon. Atoms of oxygen and silicon join together as tetrahedrons (three sided pyramids). These stack together to build crystals. Billions of tetrahedrons are needed to build even a small crystal.
Malachite and quartz are quite common so they are not overly expensive gemstones.
So there you have it! I hope you learned something new from this post. Let me know your thoughts.