Hi Chuck,
Like I said, I usually don’t write to strangers but in your notes to the “The List” you sound like a well sorted out new collector.
First, let me know if you got the big example of a common chondrite you were shopping for. Yeah, that will be a good stand in for the 80% of rocks waiting for you and your new metal detector.
Second, you ask “What are these ‘Type Threes’ people talk about?” Well, you’ve got books that explain it better than I can but here are a few words and a few pictures that might help.
You’ll find there’s a six point scale for chondrites. (We ARE talking just chondrites here.) Believe it or not it doesn’t go from 1 to 6 or even from 6 to 1. It actually goes from 3 to 6 AND from 3 to 1. The 3 to 6 part tells how much the rock has been affected by heat back home on its asteroid, from very few effects at 3 to a lot at 6. The 3 to 1 tells how much it has been affected by water before it came to earth, from very few effects at 3 to a lot at 1. You see that type 3s are the least changed by heat and the least changed by water and that is why some collectors like them. I know I do. Check out the pictures and see if they do anything for you too.
– John
This is part of a slice of the type 3 chondrite Begaa LL3. Chondrules and lithic clasts are well defined.
It’s easy to see individual chondrules in this backlit thin section.
Begaa LL3 again, this time in crossed polarized transmitted light.
It’s crowded but each part has its place with dark matrix between.
This is NOT a type 3 it is a type 6 for comparison. Chondrules have lost definition and the matrix has recrystallized from an extremely fine (hence opaque) consistency to a crystalline coarseness that transmits light. It is Estacado H6.
Estacado H6 again. It is unusual to find such a well preserved barred olivine chondrule in a much
metamorphosed meteorite. Much of the black in this view is metal.
Dhofar 535 LL-R3.3. Well defined chondrules in an opaque matrix.
Dhofar 535 LL-R3.3. Typical type 3.
Dhofar 535 LL-R3.3. Very cool barred olivine chondrule with super thick rim. The glass between the bars started to crystallize.
Detail. The rounded black spots are probably blebs of metal and/or sulfides.
A type 3 with smallish chondrules but, again, set in a dark matrix. Kainsaz CO3.2.
Kainsaz CO3.2 contains a good population of medium size chondrules too.
CV3 meteorites have rather large chondrules set in a fine grained matrix. NWA 2086 CV3.
A nice CV3 portrait. Several chondrules, a classic amoeboid olivine aggregate
and a large Calcium Aluminum Inclusion. NWA 2086 CV3.
John may be reached at john(at)johnkashuba.com
