Mr. Spock: Curious. What Chief Vanderberg said about the horta is exactly what the mother horta said to me. She found humanoid appearance revolting... but she thought she could get used to it.
Dr. McCoy: Oh, she did, did she? Now, tell me, did she happen to make any comment about those ears?
Mr. Spock: Not specifically, but I did get the distinct impression she found them the most attractive human characteristic of all. I didn't have the heart to tell her that only I have...
Captain James T. Kirk: [interrupts Spock] She really liked those ears?
Mr. Spock: Captain, the horta is a remarkably intelligent and sensitive creature... with impeccable taste.
Captain James T. Kirk: Because she approved of you?
Mr. Spock: Really, Captain, my modesty...
Captain James T. Kirk: [interrupts Spock] ... does not bear close examination, Mr. Spock. I suspect you're becoming more and more human all the time.
Mr. Spock: [surprised... a little] You... Captain, I see no reason to stand here and be insulted.
Captain James T. Kirk: [exchanges laughing glances with McCoy as Spock walks away] Ahead Warp Factor Two.
[McCoy has been ordered to help a silicon-based life form]
McCoy: You can't be serious. That thing is virtually made out of stone!
Captain James T. Kirk: Help it. Treat it.
McCoy: I'm a doctor, not a bricklayer.
Captain James T. Kirk: You're a healer. There's a patient. That's an order.
Mr. Spock: The Horta is badly wounded. It may die.
Dr. McCoy: It won't die. By golly, Jim, I'm beginning to think I can cure a rainy day.
Captain James T. Kirk: Can you help it?
Dr. McCoy: Helped it? I cured it.
Captain James T. Kirk: How?
Dr. McCoy: Well, I had the ship beam down 100 pounds of that thermal concrete. You know, the kind we use to build emergency shelters out of 'em. It's mostly silicone. So I just troweled it into the wound, and it'll act like a bandage until it heals. Take a look. It's as good as new.
Captain James T. Kirk: Well, Mr. Spock, I'm gonna have to ask you to get in touch with the Horta again. Tell her our proposition: She and her children can do all the tunneling they want, our people will remove the minerals, and each side will leave the other alone. You think she'll go for it?
Mr. Spock: It seems logical, Captain. The Horta has a very logical mind - and after close association with humans, I find that curiously refreshing.
[opening his mind-meld with the Horta]
Mr. Spock: [crying] AHH! PAIN! PAIN! PAIN!
Mr. Spock: Jim, I remind you that this is a silicon-based form of life. Dr. McCoy's medical knowledge will be totally useless.
Capt. Kirk: He is a healer, let him heal.
Mr. Spock: Captain, we are being watched.
Captain James T. Kirk: Are you sure? Intuition?
Mr. Spock: No, sir. We're being watched.
Capt. Kirk: Mr. Spock, give us a report on life beneath the surface.
Spock: Within range of our sensors, there is no life other than the accountable human residents of this colony beneath the surface. Eh, at least, no life as we know it.
Mr. Spock: Captain, there are literally thousands of these tunnels in this general area alone. Far too many to be cut by the one creature in an ordinary lifetime.
Capt. Kirk: Then we're dealing with more than one creature, despite your tricorder readings, or - we have a creature with an extremely long lifespan.
Mr. Spock: Or, it is the last of a race of creatures which made these tunnels. If so, if it is the only survivor of a dead race, to kill it would be a crime against science.
Captain James T. Kirk: [Facing the Horta] Well, what do we do, just... talk it over?
[the Horta turns to show her phaser wound]
Captain James T. Kirk: Well, you can be hurt, can't you?
[the Horta turns back]
Captain James T. Kirk: We just sit here? It's your move.
Mr. Spock: Mr. Vanderberg, what is this?
Chief Vanderberg: It's a silicon nodule. There're a million of 'em down there. No commercial value.
Mr. Spock: But a geological oddity, to say the least. Pure silicon?
Chief Vanderberg: A few trace elements. Look, we didn't call you here so you could collect rocks.
Dr. McCoy: Schmitter didn't burn to death, Jim, not in the usual sense anyway.
Captain James T. Kirk: Explain that.
Dr. McCoy: Well, there are only fragments of bone and teeth left, but the plant's physician agrees with me - a chemical corrosion, almost as if he'd been thrown into a vat of extremely corrosive acid.
Captain James T. Kirk: Strong enough to eat machinery?
Dr. McCoy: Strong enough to eat anything else the way we can think of.
Captain James T. Kirk: Mr. Spock, we seem to have been given a choice: death by asphyxiation or death by radiation poisoning.
Mr. Spock: We are dealing with a silicon creature of the deep rocks, capable of moving through solid rock as easily as we move through the air.