Dear Damien,
Have been preparing this on/off during the day.
I am very pleased to share the info., and am glad you liked the pics. and found the matter interesting. The more people who know about this place and something about them the better, it all helps to ensure their protection and preservation. I know it's off track re boats/ships, but Chit Chat does carry varied subjects so I just thought people might like to see these things... they are so mind bogglingly incredibly unique!!! It just goes to prove - yet again - that there is nothing new under the Sun!!! Had this been considered in someone's mind for construction for a film set it would probably not have been done, being thought too far fetched even for Sci-Fi!!! Here is some background info. that I keep as brief as possible.
The main cavern (one of three thus far), at the Naica Mine (Naica, Chihuahua Province, Mexico), is 1000ft below surface (not as deep as it sounds when you consider that Dolcoath Mine, Cornwall was at one kilometre in 1923 - 500m in 1820), the largest crystal is a min. of 11m in length, and weighs apx. 56 tonnes - some crystals are over 6 ft. broad, with a growth age calculated to apx. 500M years. The caverns are near - or in effect can be said to be part of - the Naica Fault, an area kept away from for quite a while due to suspicion/concern of flooding. The Main cavern temp. is 50C, with humidity at 100% so this is obviously human lethal in a short space of time (as one miner nearly found out not long after it was found - shouldn't have been there anyway). Even with custom breathing gear and wrap coolers, 20mins. is the max. stay duration, but it is still very body 'difficult'/stressful. The mine as a whole is hot anyway, and kept to 40C - 45C with humidity at apx. 50% by, what are in effect, large air conditioning plants - on similar lines to the deep S.African Au/dia. mine units.
One of the prev. large caverns found is lined with metre length 'spear' crystals over it's surfaces, and another is slightly smaller but has different formations (heavy clusters and 'sheets' as opposed to spears). The crystal structure variation between caverns is due to different hydrothermal flow and cooling parameters: there is a magma heat source at apx. 3km below, so it's a question of where the source flows originate for each chamber - basically how close to the heat (& mineralising), source and the ascending route. It is strongly suspected there are other caverns to be found since (& while), the geology remains constant, so, whether this mine becomes a UNESCO / World Natural Heritage site or continues with lead/silver/zinc production (both or three!), remains to be seen. (Personally I would like to see UNESCO fund Ground Probing Radar surveys to test for voids ahead and below any underground development levels, likewise geophysics in whatever form(s) might be considered appropriate for any given situation). The problem is it is a very productive mine and obviously gives much employment, so you can't just stop it... at the same time it must not be forgotten that it was the mining opers. in the first place that found everything, so if carefully proceeded with it is probably best that production and development continues. All mines eventually become worked out of course, so it's a question of how can the caverns/crystals and mining coexist happily until exhaustion is reached. After mining finishes, there is then the problem/cost of pumping water (apx. 16k gallons/min. inflow), and who is going to pay that cost? If of course more caverns were to be found, there is little doubt that the Naica Mine could be made into a very important International academic and tourist facility, and might well pay most of it's way after a set-up period - it certainly would if Corporate sponsorship was sought to back up any UNESCO funding.
So, all in all, the place has hopefully a very interesting future indeed: the caverns and crystals are being well looked after in the meantime by many academic and professional bodies/people, and, the mining Co. (Penoles), deserves much accolade for being very responsible, considerate, and accommodating - indeed a fine example to other mining Co's who have destroyed countless tons of world class mineral examples, when, with just a little effort and added expense they could have been saved/mined - and at profit as well.
I hope you and maybe some others might find this interesting. As-&-when any news filters down to me about other finds, etc., etc., I will update. Here is another interesting Link:
http://www.minsocam.org/MSA/collectors_corner/arc/naicagyp.htm For the technically minded, please find below a brief paper on the deposit.
Regards, Bernard
Compositionally distinct, saline hydrothermal solutions, Naica Mine, Chihuahua, Mexico
R. J. Erwood, S. E. Kesler, and P. L. Cloke
Univ. Toronto, Dep. Geol., Toronto, Ont., Canada
Naica is a chimney-manto, limestone-replacement, skarn-sulfide deposit typical of those that have yielded much of the silver, lead, and zinc production of the western hemisphere. Fluid inclusions in fluorite deposited throughout late skarn and most sulfide mineralization at Naica provide the first direct observations of main-stage fluids in these deposits. The inclusions can be divided into three compositionally distinct groups: (A) liquid + vapor (119 degrees -379 degrees C homogenization temperatures), (B) liquid + vapor + halite (237 degrees -- 369 degrees C; salinities of 31-43 equiv. wt % NaCl containing less than 12% KCl); (C) liquid + vapor + halite + sylvite (277 degrees - 490 degrees C; 52-63 equiv. wt % NaCl containing 22-31% KCl) with some high temperature inclusions (565 degrees -684 degrees C; approximately 40 equiv. wt % NaCl with approximately 25% KCl). Types A, low-salinity B, and high-temperature C inclusions homogenize by vapor disappearance. High-salinity type B and most type C inclusions homogenize by halite disappearance. Evidence for boiling is seen in type A and low-salinity type B inclusions.Types A, B, and C inclusion solutions occupy relatively small, compositionally distinct fields in the NaCl-KCl-H 2 O system. High-salinity type B and most type C solutions were apparently saturated with halite. The composition of high-temperature, unsaturated type C solutions could have been controlled by equilibration with granitic rock and that of saturated, low-temperature solutions could have been controlled by halite subtraction. Wide and completely overlapping spatial distribution of all three inclusion types, combined with the fact that all three solutions are fully miscible, requires that the three compositionally distinct solutions were present in the deposit at different times. The most likely order of appearance of the solutions was C, then B, and finally A with pressures considerably above lithostatic during C solution activity, lower but still exceeding lithostatic during early B activity, and hydrostatic during late B and throughout A time.
This record provided courtesy of AGI/GeoRef.