. . . and corresponding Mastcam-Z left eye filter 0 (RGB) enhanced image and multispectral images

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The value of the PCA color effect is that it makes it dramatically clear when color similarities and differences in an image are significant (statistically) but perhaps not different enough for the human eye to see the similarities and differences.

For an artificial example, suppose there's an image that had an RGB of 128, 87, 23 across the entire upper left and 128, 84, 23 across the rest of the image. The human eye would probably see no difference at all. Statistically, the difference is significant. The PCA algorithm would, I think, make a strong difference between those two areas.

As for what that means geologically, that could be anywhere from nothing to everything.

An example that I've mentioned before: The colored (usually radial) patterns seen when there's oil on a wet street indicate absolutely nothing about composition. It only indicates a truly microscopic gradient in the thickness of the oil on the water. But the color differences are dramatic. Nature never guarantees us that color means compositional differences.

But:
1) Detailed spectra can provide compelling, even overwhelming evidence of composition, especially with gases and vapor. For example, we can be absolutely certain that Uranus and Neptune have methane in their atmospheres.
2) Withstanding all of those disclaimers, color of low spectral resolution sometimes is absolutely due to a compositional reason. If we sprinkled graphite powder all over the floor of a room and then sprinkled sulfur powder on top of that in one corner of the room, that color difference would 100% be due to composition.

I'm sure that in many of tau's PCA colored images, a particular color maps onto a particular kind of composition. But it's another thing to know when that's true and when it's not. That's beyond my knowledge of geology.

If you mean in all of the images for which tau has mapped colors onto principal component outputs, then there's no guarantee of that, and at best it would be coincidental. That could be true in one image taken in the morning and then not true in another image taken of the same landscape that afternoon.

If you mean in that particular image, also no guarantee. The color filters in the first place don't have the spectral resolution to determine composition. But, again, it could be true coincidentally in any one image, but we can't infer that everything blue must be basalt.

Sol 912 Mastcam-Z left eye filter 0 raw image (black frame omitted), filter 0 image enhanced, and filters 1 to 6 multispectral principal components

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This image, and the ones posted by Tau, are clearly a coarse, poured-in sediment that is angular and poorly-sorted.

Sol 464 Mastcam-Z
1. Left eye raw image
2. Left eye filters 1 to 6 multispectral principal components
Judging by the multispectral false colors, the conglomerate in the upper halfth of the image consists of a variety of different rock types an minerals.

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Sol 436 SuperCam Remote Micro-Imager mosaic with Mastcam-Z context and sol 435 Navcam context.
The bright stripe at the lower edge of the SuperCam mosaic is part of the so-called "Bacon stripe" at Hawksbill Gap.

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More layered outcrops at the base of Cape Nukshak in Mastcam-Z images from sol 423
1. Raw image filter 0 (RGB)
2. Left eye filters 1 to 6 multispectral principal components. A few stones have alternating blue/purple layers.
3. Right eye infrared filters 1 to 6 multispectral principal components 1 and 2
4. Anaglyph

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Sol 420 Supercam Remote Micro-Imager mosaic with sol 419 Navcam context
The mosaic shows the upper right corner of the sol 419 Mastcam-Z multispectral photo (see post #27), but from a slightly different perspective.

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97 new Mastcam-Z raw images of the delta from sol 306 just arrived.
Here are three of them, specially selected for the "inner sedimentologist" of Saturns Moon Titan, in a processed version.
A note for new visitors: the blue color of some of the stones in the images is due to color enhancement. In reality they are more gray or brownish gray.

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