Dear Will, Thanks for your input on beach gravels. I basically agree
with most of your assertions, but I would not agree as to their
relevance to the Central Calfornia Coast. There is no evidence locally
that the beach gravels have their origin in anything other than
nearby sources. Everything that I have found on the beach is easily
traced to the strata upstream. As for the possibility of subducted
conglomerates realeasing cobbles, it is my opinion that these cobbles
probably would not have survived the trauma of subduction at
depth.One of the commonest forms of rock locally is the bresciated
jaspers which have obviously been reworked and recemented after
crushing. The assumption that these same rocks are the product of
metamorphosis of the local strata is clearly apparent. Yes, Morro Bay
is undergoing rapid sedimentation and filling. Whether the time frame
is valid is another consideration. The latest factor which might
affect the time frame would be the fact that the oceans are rising
rapidly as a result of polar ice loss. If you were to project the
latter phonmenon, it is quite possible that we will eventually see
estuaries and bays where there were none ! Maybe the survivalists
should be stashing wet suits ! Ron at Mills Gem, Los Osos, CA.
will wrote:
Will, Some of the cobbles from Carlsbad (San Diego County) down into
Guatemala are a form of Jade, and at this time presumed to be Mantle
origin. Many contain precious metal inclusions such as platinum, gold
and platinum gold as well as silver. I have watched as the gold was
separated out onto silver anodes from slurry after cabbing.
These make up into wonderful cabs and polish up to a high sheen. Some
of our club members are casting in situ. They will take up to 2000
farenheit.
Have you seen any papers on this? Thanks, Teresa
Dear Peter, Once again the voice of wisdom without parading titles,
put downs, or using multi-syllables for effect rather than content.
One need just once to stand at the Grand Canyon to see the cutting
ability of water. Where we have well intentioned persons from many
countries offering suggestions to the best of their ability in a
language foreign to them, we must reply with respect. The majority of
posts here are well intentioned, from wonderful people, with only the
best in mind. It is only those who feel they know it all and have
nothing to learn, that rocks the apple cart.
I love the International quality on Orchid, the incredible sharing
and caring. Please let us not lose that with elitist, imperious
commentary. It is very easy to hurt with words, especially directed
upon those not used to our colloquialisms.
I cannot hammer blow damage to a jade cobble, but slab and
accidentally drop and watch it shatter, I can do easily. There are far
too many high tech treatments done to stones today that change the
characteristics in unknown ways. The faceting posts indicate over and
over differences now that were not known a few years ago. Heat treat,
dye, irradiate, all lead to a change in final phase, and many
surprises do occur.
You Peter are a gentleman through and through. Thank you.
Teresa
Hi Teresa, Wow, I haven’t seen any of the “jade” from Carlsbad,
especially any mantle material. I know that there are records of jade
found in S. California and I have one sample of nephrite from the
hills near Escondido. The only mantle material I am familiar with is a
little outcrop of eclogite near Muir Beach, and a garnet peridotite
from Prescott Arizona. They are rare. I will look into the material
you describe and get back to you if I find out anything, Regards, Will
E.
PS. I agree with your post re Peter, He is a gentleman.