Hi everyone,
I'm pretty new to bonsai, however I have a few trees. I recently purchased one from a bonsai nursary, and wishing about a week or so, the leaves started to get really hard, and crumbled when I touched them. They also went a very dull green. I have another Chinese elm (that I bought from Bunnings of all places) and its leaves are bright green and don't crumble when I pinch or touch them. I'm beginning to think that the woman sold me a dying tree.
Any thoughts on why the leaves are doing this? Any help will be appreciated!

What country are you in? If you have it inside are you watering it and if so how? Sounds to me like it is dry, leaves will die if the tree is lacking in water. If the tree was in a cooler place and you took it to a much warmer place that will not help. This species is hardy and is best kept cold in winter. Mine are outside and at this moment the temp is just above freezing, and the still have leaves.
You need to check to see if it is dry with a chopstick, if it comes out clean then it needs water. Soak well and allow to drain. Then check every day and water when almost dry,
Geoff.

I'm in Australia and we're in the middle of summer. I leave them outside, but I bring my bonsai's inside if it gets too hot (30°c and above). I water it when the top soil begins to go dry, and I only water it till water starts coming out the drainage hole. I think that what you said about its previous placing has something to do with it. The nursery I bought it from kept them inside, but I placed it outside with my other trees. However, I keep all my bonsai's in the shade except for a few hours in the morning were I put them in full sunlight. The sun in Australia can be pretty harsh so I try to avoid putting them in the sun for too long.

OK, well, the best place is out, however I think you are doing the right thing by shading it in the heat. It should be fine as long as it has enough water. I would think you might be watering at least trice a day if not more. That is what we have to do and it does not get that hot.
When I water I go around all my trees and then go around again if it is hot. That way I make sure that the water gets to all the soil,
I think the tree should be ok, you could try spraying to up the humidity and watch for new buds,
Geoff.