Please forgive me if this is not specific to gemstones, but I think it is relevant and I am curious to hear others thoughts on this.
Over the past couple of decades, it is becoming more and more clear that microorganisms (bacteria, largely) play a central role in the formation of minerals, and a number of other geological processes (erosion, etc). To date, geological theory has focused on geothermal and non-biological processes (heat, pressure, etc.) but multiple papers are published each year which challenge that theory, or at least suggest a need to rethink many of the fundamental assumptions of that field of science. For additional information search “MICP” (microbial induced calcite precipitation) or simply “biomineralization”.
The relevance to gemstones I believe is significant. Since gemology rests largely on geological theory, and it is becoming clear that bacteria/microorganisms almost certainly played a significant role in the formation of minerals/gemstones, it will likely prompt revisions to everything from mining, to synthetic synthesis of gemstones, to various theories related to gemstones themselves.
I recognize this is a touchy subject in the field of geology, and I do not want to stir up non-constructive discussion, but I am curious to hear if this emerging research has found its way into the field of gemology, or if anyone has perspective on its potential impact.
Although “biomineralization” is very real, all the professional papers in support of this process are related to surface conditions and the formation of non-gem minerals… mostly calcium phosphates and carbonates. Most of the gem minerals we love (ruby, sapphire, diamond, tourmaline, topaz, garnets…etc.) have NOT been the subject of biomineralization because the thermodynamic data is overwhelming that the stability fields for their formation are indeed high temperatures and often high pressure. I find your statement of “multiple papers are published each year which challenge that theory” is just not correct… none of the studies you cited are questioning the hydrothermal, igneous, or metamorphic origins of the vast majority of gemstones that we enjoy working with in our society.
I like Newton’s statement…“If I have seen farther than others, it is because I have stood on the shoulders of giants”. New directions in science rarely negate previous sound research, but are built by extending the earlier results into unknown areas. The thermodynamics used in current biomineralization are built upon the same principles that were established in the research of the formation and stability of gemstone… the new direction is not producing contradictory or alternative origins for gems… but is exploring the field of low temperature (and low pressure) mineral formation by living organisms… This is a new field that is NOT questioning the well established processes of gemstone formaion.
Thank you for the thoughtful reply, I appreciate your perspective. I certainly do not want to stir up controversy, I know this can be a touchy thing in geology. I certainly could have chosen differently terms in my post, but I am pretty confident the points I made are quite well supported by the research. Microbes and bacteria are indeed essential to a great number of geological processes that were once thought to be geothermal (ie, non-biological, in this sense). That is not to say that geothermal, climatic, etc. forces are not also essential factors in mineral formation (and processes like erosion, etc), I hope that was not how my post reads. My point is/was roughly that these non-biological factors are not at all sufficient to explain a a great number of such processes, including the bio mineralization of a rapidly glowing list of minerals, many of which are indeed considered “gemstone” or gemstone minerals (agate, carnelian, and even pearls, to name a few - see bottom link). The thing with discoveries like this is not so much the current state of knowledge (in this case of the absolute number of minerals and processes with essential biological dimensions), but the trend. Here’s a rough sense of those trends from Pubmed, the first a chart of the publication of papers on bio mineralization, the second on MICP (microbial induced calcite precipitation, a subset of the former, as I’m using the terms:
Of course, theae papers cover more than just gemstones or even minerals, but that speaks to the growing awareness of the breath of such processes, which is hard to really dismiss, IMHO.
It’s interesting to me that the role of microbes in the production of minerals and other hard, mineral like processes was quite well known in ancient times (Strabo and Horodotus both describe it, but not using thai term), so it’s not new knowledge, nor does it seem particularly controversial. I guess I was just interested in hearing what others may think of this topic in the gemstone world, and I appreciate your reply.
Here’s a few papers, just by way of context. There are many (I understated the number by using “yearly” in that sentence), and it’s a fascinating field:
Pearls are indeed a biomineralized example of carbonate (85+% CaCO3). Coral is another and bacterial interaction is certainly not excluded as a component. I did my PhD in part on neo-diagenesis and found a clear link between organic matter and the precipitation of clays in very young sediment (bacteria are directly involved in this process).
However, this is not the same as the usual gem minerals like diamonds, emeralds, sapphires, garnets, etc… that are typically formed at temperatures higher than bacteria can survive. Agate, carnelian, and opal are all variants of quartz which can form under a range of temps from way too hot to just right for bacterial interaction. And, bacteria do interact with iron and sulfate mineralization at surface conditions and at depth. Nonetheless, most of what the folks on this site would call precious gems are formed at high temps (too high for bacteria).
Hi, thanks for the reply, it’s still a topic that interests me a lot, and I’ve done quite a bit of research on the topic (i’ll probably write a paper one of these days on the topic).
I’m not sure I agree with you, though. Since posting this, I’ve found pretty extensive ancient textual references to this process specifically, although the biology was not known as such, the process was as far more widely known than I would have guessed. Temperatures are not quite relevant in the sense that I think you are framing your reply. That is, although bacteria can survive on an astroid or in acid (and in very high temperatures), as a biological process, such high temperatures are not a factor, and to my knowledge, such processes can occur pretty much anywhere on earth (in any environment). I even tried it in my basement, it’s not at all difficult, and made something approximately basalt, it’s remarkably hard (density wise). Admittedly, that’s not a gemstone (although I’m quite pleased with the results, lol), but most known grow-able crystals do not require particularly high temps, and they don’t even require lab conditions, mother nature does most of the heavy lifting.
I think it’s hard to argue, just given the statistical rate of discovery of the central role of such processes versus the finite number of known minerals, that it’s just a matter of time before most, of not all, including gemstones, are understood to involve biological processes. That’s not my opinions, it’s sort of how the math works out. Anyhow, if you are interested I can forward the paper when it’s done. Thanks again!
Paul,
Interesting… Can you please list the precious gem minerals that form at low temperatures or surface conditions and that have documentable bacterial mediation for their formation? For carbonates, sulfates(ides), silica (including opal), and numerous other minerals that may not be considered precious gems… we may easily agree on a number of these minerals being bacterially mediated at temperatures bacteria can do their thing. When we get to garnet, tanzanite, topaz sapphire, emerald, diamond, etc… maybe not so much. Mother nature tends to do the heavy work with temperature and pressure for these (the lowest documented formation temps for these minerals is ~700 degrees F and higher (>melting point of lead). If you can do so with the right mix of bugs in your basement, there will be a LOT of folks here who will be extremely interested to see your results!
