While I'm fine with Jaleon abusing her slaves as a way to set her character, I got bored of her abusin Jin fairly quickly. She spends several pages doing it, right off the bat, and uses most of the same insults.
Also, she seemed to go fairly quickly from insults to wanting to kill something (Jin). While I can (though I don't know, because this isn't an aspect of her character that you've touched on so far) that she doesn't think of slaves as people, and that killing one therefore isn't a big deal, I can't imagine her doing very well as a slave trainer if she kills every slave that annoys her. Slaves, after all, cost money.
Also on the subject of Jaleon: The inconsistency in spelling her name. Sometimes it's Jaleon, sometimes it's Jalean.
When you describe the crest that the soldiers from Maz's caravan are wearing, you pass up a really great opportunity to describe the murt, which has come up a few times by this point. You describe the crest as having a beast "like" a murt, and while you do a fairly good job of describing the rest of the crest, that particular bit of information is meaningless to us.
I have to agree with Cynic, though, I really enjoyed the description of the caravan in general (though I'm also right with Cynic in wondering why such a display was put on for simple slavers).
I have to agree with Cynic on a couple of other points, too; a little bit of clarification (it probably wouldn't take much) on what happened with the sparks--and maybe some reaction from Burm that tells us a little bit about how common this sort of ability is or whether others (like Burm) knew he had it. And I also wondered (though I was kind of on the fence about it) if the self-pity at the end might be little too much. I certainly empathize with Jin's feelings that being sold might not be a good thing, but is there also some small relief that he's away from Jaleon, some bit of hope that things will be better, something? Actually, including those emotions could be a big help even if you don't lose the self-pity bits at the end. People can certainly have emotions that conflict with one another.
I'm not... entirely sure I buy the way Maz recognized Burm, particularly right off the bat (unless there's something to this reunion that we don't know). But for a chance caravan coming in off the road, it seems like a huge coincidence.
From the way Jaleon treated Maz, I'm guessing she must be someone that Jaleon has a lot of respect for, and at the moment I'm thinking that it's a personal respect rather than (or only) respect for Maz's social position. I'm leaning this way mostly because Jaleon didn't just bite her lip and sell Jin for as high a price as she could manage.
Why was Jaleon the one dressing Jin up and, especially, scarring his cheeks? Since Jin belongs to Maz now, shouldn't Maz be the one overseeing that?
Maz remarks that Herme isn't actually related to Jin and "neither is the man Jin calls father". I'm unclear on this; I thought that Herme WAS Jin's father. Or perhaps I should say that Jin thought Herme was his father.
I thought Jin was older than ten; I would have put him in his early teens, at least, but I thought I saw something in the text that suggested he was twelve, but your email says ten, so... Yeah. He doesn't read at all like a ten-year-old (though I could accept him sounding a little older than his age, considering his situation). Also, if he's so young I don't quite understand why everyone is giving him such a hard time about being weak and whatnot. Even if he's tall for his age, it seems kind of ... short-sighted.
RE grit: I did find her fascination with Jin's, ahem, parts a little bit annoying after a while--though I appreciated that Jin found it bizarre too. I'm not sure if it was the actual content here that bugged me, or just the repetition that I mentioned above. Either way, I certainly don't think it should go away. But you can safely tone it down a bit, I think.
I thought the bluntness regarding sex was interesting too (though it's true we don't see much else of the women. I'm willing to let that slide for now since we haven't seen much of the women at all. It does kind of seem like it's ONLY the women, but then, we only see two boys in this scene: Jin and, much more minimally, Burm). I don't even mind it in Maz's daughter, depending on her age (because right now I have no idea). If she's mid-teens or older, than that's fine. If she's closer to Jin's age, then I think Frog is right and you do have a problem. (I've been a ten-year-old girl, so I think I can safely say that they REALLY don't care about those things.)
I didn't think that the over-sexualized aspects of the society were particularly female (remember, we haven't seen many of the men yet), nor did I think they were really that overly sexualized, just not reticent about expressing their thoughts on the matter. I WOULD be leery of the society where females are totally in power and nothing but walking sex drives, because aside from perpetuating a not-very-nice stereotype it most certainly has been done before (RA Salvatore's drow society comes to mind), but I don't think that there's anything wrong with characters just being blunt about sex.
A little more description about the environment, like the Pits themselves, could definitely be helpful. Also, at least SOME passing reference to people who aren't the slavers, Jin, or Burm. Before Maz and her company show up, I seriously don't think we get ONE mention of a person who is not Jin, Burm or Jaleon; not even as objects in space. I don't think you have to spend much time on either of these things; even a couple of well-placed sentences could potentially fix that up.
Anyway. Overall, I enjoyed the piece. I'm interested in the premise and curious to know what happens next, so good work there. I think your biggest hurdle in this chapter is the opening scene (Jaleon abusing Jin) which, as I mentioned, I found a little long. It seems like all these things I (and others) have been mentioning are fairly easy fixes, though. So good luck!