Chlorite in there somewhere

Chlorite announces its presence in a rock by giving it an appearance of moldy bread. Other than that, chlorite is too fine-grained to be seen other than in a high power microsope.

This cobble of a phyllitic sedimentary breccia from the Aliakmon River is full of chlorite.

If you saw this in your bread box, you'd chuck it. 

Mylonitic Limestone

This is what limestone looks like after a rather large ophiolite mashes it.

The field of view is about 5 cm. 

What's left --

--of a piece of 270 million year old gneiss after its been rolling around in the Aliakmon River for who knows how long.

This cobble of lineated gneiss has weathered so that each feldspar grain stands out on the surface, and the "softer" mafic minerals weather away around them. The result looks like petrified rice. Each white grain is about 0.5 cm long. 

Sulfide Accessories --

These add a lot to a rock's appearance, don't you think?

Pyrite, silvery shiny in center and right, is in a matrix of quartz, with colorful secondary sulfide minerals (mainly sphalerite) coating the rock surface.

A piece of "stockwork zone" from a hydrothermal system in the Pindos Ophiolite. 

Garnets for Dina --

Width of view of the meta-gabbro is about 3 cm. I didn't notice the red-brouwn garnets, some of which have euhedral-ish outlines, until I made this scan and it became apparent that they were translucent.

The white masses are altered feldspar, most likey "rodingite" also a kind of massive garnet. The black grains are amphibole, some of which are very lath like in form. 

A single Pyroxene Crystal

Orthopyroxene as a matter of fact.

I've outlined it from rest of the rock, just to emphasize its shape "in the wild."

The length is about 12 cm.

PS. You really can't tell ortho from clinopyroxene ALL the time. Usually the clino is darker, and the ortho is lighter in color. 

Pyroxenite

Pyroxenite is, not surprisingly, composed of pyroxene -- in this case, both orthopyroxene (brownish) and clinopyroxene (blackish).

At the source outcrop on the Aliakmon, some crystals reach nearly a meter in length.

The width of this photo is about 12 cm. 

Zeolites

Bob's little sample from the Aliakmon.

The radiating crystals are characteristic of zeolite, but what sort of zeolite, remains unknown for now. The diameter of the largest radiating mass is about 0.3 cm.

Note the Zeolites, in a vein, that cross cuts older black veinlets of serpentine in (yet older) a pervasively serpentinized peridotite. 

Incredible Quartzite

This is a flake from a quartzite cobble that caught my eye along side a road; it's a bit of road-building talus, nothing more.

But opened up -- translucent, it looks more like ice than quartz.

This certainly demonstrates that even the most mundane rock lying around contains an incredible inner beauty. 

Not Surprisingly Sandstone

Pentalofos Sandstone from here in Greece. It looks, not surprisingly, like sand on a beach of today, but is indeed about 60 million years old.

Borrowed from the earth, this is the traditional building stone for houses, churches and bridges all over Northern Greece, some of theses structures dating to the Byzantine Period.

History built on a historic stone.

Width of the photo is 7 cm. 

Oil Shale with Fish

Green River Formation, not Greece.

Eocene (~50 million years old or so) fish, in carbonate matrix siltstone, glopped over by petroleum.

It smells, but not of rotten fish.

Fish is 10 cm long. 

Gabbro!

And pretty fresh at that, considering where we found it.

A cobble in the Aliakmon, miles and miles away from any source of fresh gabbro.

On this surface, the milky crystals are plagioclase cut at some angle that you can see their twinning, while one crystal (top center) does have visible twinning. The dark mass in the center is clinopyroxene, and actually looks better in real life, with visible cleavage reflecting when the light is held the right way.

The pyroxene cystal is about 1.5 cm scale, making this actually a gabbro pegmatite. 

Mylonitic Peridotite

Or at least is once was, since except for the chromite grains (black-redblack grains, the largest about 0.5 cm across), the other phases are serpentinized, and the rock is crossed by green veins of serpentine.

A strong foliation is apparent on the scanned surface, this part of a mylonitic deformation that affected the rock long before the serpentinization took place. Peridotites of this appearance were deformed at temperatures of around 1000 C. 

Just a bit of amythyst.

Okay, okay, it's a pretty rock.

Even geologists like pretty rocks.

Note the lovely crystal forms, totally characteristic of quartz, and the color, totally amythystic.

The "large" white crystal with purple tip on the far right is about a cm long. 

Well, schist!

Back to basics, a real rock.

The photo is about 4 cm wide.

Dark gray crystalline areas are, indeed, quartz. Whiter areas are not, but seem to be feldspar, or an altered growth of ex-feldspars. Brownish patches are essentially intergrown amphiboles. That's about all there is in this rock.

It's horrendously deformed, the white elongate bleb in the upper center essentially is a "boudin" of its former self. 

Silicified Diabase

This may look like flint, and if it weren't from within an outcrop of silicified lavas in the Pindos ophiolite, you'd certainly think it was.

The archeologists are always asking if I know of a green-colored chert or flint that stone tools may have been made from, and this certainly would fit the bill. So fine grained as to have lovely choncoidal fracture. Several manganese "kisses" on the surface. The larger cluster of minerals in the center and on the lower right margin are clusters of small quartz crystals. 

Cretaceous Snail Guts

This is a view looking down the innards of an eighty million year old snail, one of the giant rudistids of Greece.

The entire snail was tusk-shaped, and over 50 cm in length, about 12 in diameter. This view is about 4 cm wide, looking right down its fossilized gullet, hah! Do you suppose all the little bits of shell in the black matrix are remnant of its last supper?

It's now part of the Orliakas Limestone unit. 

Manganese dendrites...

...on Manganese marble.

The pink colof of the carbonates is a dead giveaway for the presence of more manganese than normal in the marble. The dendrites are water-born seeps of manganese into fractures that, when the water leaves, crystallize into forms resembling plants and branches. The width of the photo is about 4 cm.

Serpentine

Well, serpentinized harzburgite to be precise. Serpentine is an alteration of ultramafic rocks.

In this rock, you can see the minerals, or ex-minerals as the case may be:

Small (mm scale) black grains = chromite, and these are not serpentinized.

Blue-grey boxy-shaped grains with cleavage lines = orthopyroxene that has been serpentinized.

Yellow-brown-orange patches = serpentinized olivine.

Black almost glassy veins cutting everything like a mosaic = serpentine.

I never care much that these sorts of rocks are serpentinized, and generally map them as their protolith, harzburgite, that gives me more information about what's gone on. Some geologists map entire mountains as serpentine, even though its often more important to know what the rock was before it was serpentinized. 

Mica in Marble ..

Ethereal, isn't it?

This is a marble schist, not just because of the mica, but because there is quartz (grey grains) in the background field of white marble.

But the Mica is the star attraction, just a lovely, though totally worthless, stone.

The sample is about 5 cm square. 

What's in Muck

These are bits of leaves and other plant fragments in a matrix of clay and quartz sand. Mostly clay (green). The white blebs are sand.
The size of the largest leaf remnant in the center is about 0.5 cm.

The black color of the fragments and green color of the host rock indicate reducing conditions, no oxygen present. In greater concentration, these could give rise to coal deposits.

Age of rock is about 35 million years. From the Mesohellenic Trough, near Tsouliakas, Greece.