I just did a search, " is there silica in Teak wood", and it said that Teak naturally has Silica in it, and can cause blunting in cutting tools. But, as I said, I cut Locust all the time and it dulls a saw no faster than any other wood. But, some types of Locust have very deep bark and if it was skidded out of the woods, the bark is going to be packed with dirt. If I have to cut up a log I cut most of the way through, then roll it over and stick the bar in the cut and under cut it the rest of the way through. That way it's cutting the wood first and the dirty bark last, hopefully breaking through the bark before it spins 12,000 RPM in the packed in dirt. If you roll it over and see chunks of dirt you will have to cut through to finish the cut, take an ax and chop the dirt out. If I have a long log and have made cuts all the way from end to end, and can't roll it over, I take a small saw with say a 16" bar, and slowly cut through every fourth or fifth block, to make short logs I can roll. I cut slowly so it barely touches the ground, and hopefully won't dull before I'm done, But, I use it as a sacrificial chain. I'd rather dull a small 3/8's chain than 114 link big 404 chain. My wife's aunt and uncle live about 5 minutes from Raleigh/Durham Airport and I've cut lots of trees for them and see no difference from trees I cut in MD. I grew up in a 4th generation tree care family. One of the first things you learn is a saw will cut wood for days and not dull much, unless you hit dirt, then it dulls fast. I'm talking cutting firewood, not milling. Milling is a whole different story. Please understand, I'm not trying to talk down to you. I just don't know you or your skill level. The best way I can put what a little dirt does to a chain is, take a brand new razor, rub the blade on your concrete side walk 3 times, then go shave with it. If you are cutting up a log and break through into the dirt for 1/2 a second, and then do that ten times, it's like running your chain on the sidewalk for 5 seconds, at 10-12,000 RPM. As for sparks flying from the bar, I've seen them in daylight, cutting up brush with a loose chain. Figured it was from the chain flopping back and forth and rubbing on the inside edges of the bar. Tightened up the chain and no more problem. But, don't over tighten the chain, that will burn it up and definitely cause sparks. I've hit metal and seen sparks fly, instant dull. Do a self check and cut up a log on the ground like you usually do, then walk down the other side and see if there are any lines in the grass or dirt where you nicked the ground. That's the biggest cause of a fast dulling saw for a new guy. Not trying to lecture, I just saw you were new here, and hoped I could help.