Dear Jayson

Hi I think they can be intermediate or acidic volcanic and volcanosedimentary rocks such as Rhyolite, Dacite , Andesite and related tuffs to these rocks.

With best wishes

Dr Gholamreza Fotoohi Rad

Dear Jayson,

Hi I think they can be pumice.

With best wishes

Morovvat Faridazad

I think they are scoria

Scoria differs from pumice, another vesicular volcanic rock, in having larger vesicles and thicker vesicle walls, and hence is denser. The difference is probably the result of lower magma viscosity, allowing rapid volatile diffusion, bubble growth, coalescence, and bursting.

Formation[edit]

📷Pine trees growing on the slope of Cinder Cone, a volcanic cone of scoria in Lassen Volcanic National Park, California

As rising magma encounters lower pressures, dissolved gases are able to exsolve and form vesicles. Some of the vesicles are trapped when the magma chills and solidifies. Vesicles are usually small, spheroidal and do not impinge upon one another; instead, they open into one another with little distortion.

Volcanic cones of scoria can be left behind after eruptions, usually forming mountains with a crater at the summit. An example is Maungarei in Auckland, New Zealand, which like Te Tatua-a-Riukiuta in the south of the same city has been extensively quarried. Quincan, a unique variety of scoria, is quarried at Mount Quincan in Far North Queensland, Australia.

Uses[edit]

📷Tuff moai with red scoria pukao on its head

Scoria is used for a variety of purposes. It is commonly mined for use as loose construction aggregate in Europe, the Southwestern United States, and Japan. Another major use of cinders is in manufacture of concrete and cinder blocks.

Scoria is also used in the construction of flexible, long-lasting roadbeds, due to its high strength and high angles of internal friction. Because of its good insulating properties, such roadbeds protect the ground beneath them from frost heave and heat deformation.[7] It is also spread as a traction aid on ice- and snow-covered roads, and around oil wells to firm up mud produced by heavy truck traffic.

Scoria is used in horticulture. Because it can hold water in its vesicles and in the pore space between grains in aggregates, it can improve the water-holding capacity of planting soils. When sorted to specific sizes and tightly packed, it is also an effective barrier against tunneling pests such as termites.[7] Its striking colours and water-holding properties can make it attractive for landscaping and drainage works.[8]

Scoria can be used for high-temperature insulation, as in gas barbecue grills.[9]

The ancient Romans used cinders as construction aggregates, one of the earliest industrial uses of volcanic rocks.[7] On Rapa Nui/Easter Island, the quarry of Puna Pau was the source of reddish scoria used to carve the pukao (topknots) for the famous moai statues, and even for the main bodies of some moai.

I agree with farhood that this rock is scoria, which is typically basaltic in composition ( High in iron and magnesium and relatively low in aluminum and silica). His explanation of how it forms is excellent.

Martin Steinpress which of the two attached picture was scoria?

It seems is a riolite (we do not have the it outcrope) it have to have strate form...

If you come with me to the zone where I wrote my MsC project... you can buy andezite, riolite lavar ocks an if we have luck can collect agates

Regards,

Laszlo

Laszlo, are they similar to the lunar analog regolith?

Dear Jayson F. Enciso ,

You have right... , but this is a generic term in which the riolit tufa fits very well. Often, lithological terms, if they are not sufficiently systematized, give rise to misunderstandings. As for what is on the other celestial body, we must be doubtful... When those who inform us are often deliberately trying to mislead us.​ If you have your samples. And you've seen where they come from, then you're the best at determining what it is.

I wish you and for question follower Happy New Year!

Laszlo

It is a lapilli-sized angular pyroclastic material with little or no aquatic reworking gone through. Due to the pristine black and red alteration color the Fe content seems to be rather high. It is a scoria which in part is highly vesicular and likely to have been derived from a nearby gaseous volcanic ejection process of an intermediate to basic magma. Without precise textural and structural data collected at outcrop no further genetic explanations is possible on my part.

HGD

ok

Dear Prof Harald G. Dill ,

Thank you, the description is very good... I have not practiced my profession for twenty-five years. The enrichment with iron took place before the eruption , the phenomenon is due to surface erosion...

Regards,

Laszlo

Dear Jayson F. Enciso: the fresh samples shown have a light gray color, so they could be anything from trachyte to dacite, perhaps even rhyolite or phonolite. To know exactly which type of lava rock are present a few thin sections must be made and studied at the petrographic microscope, there's no other simple way. If you get the thin sections done and obtain some photomicrographs of them, you can send them to me and I'll be please to study them and tell you the name of the lava (or lavas) present in your area. But in thin section, as these are aphanitic rocks! Regards, Sebastian.

I see both samples as pyroclastic volcanic rocks,not as lava flows.

So these pyroclastic volcanic rocks are of low density rock because of air/steam ejection.

Better to confirm either of the samples belongs to lava flows or not flows.

Regards

Ijaz

Surely, the fragmented nature of those rocks points to a lapilli or breccia of felsic to intermediate composition. But without microscopic petrography is impossible to tell which is the composition of these fragments. Regards, Sebastian.

OK