You're talking about driveways, right? As in your zoning says you can have either a concrete drive, an asphalt one or a sand & gravel one?
Gravel is crushed rock, and they say "sand and gravel" because gravel almost always has sand in it. Crushed loose bedrock would be fine.
Concrete
Plucking is the removal of pieces of rock from a bedrock face that is in contact with glacier ice.
Gravel is a physical label for small rock fragments. Gravel can be produced by crushing of any rock type, i.e., metamorphic, sedimentary, or igneous, or can be obtained from vast deposits left by glacial means, which normally require a mechanical sorting for required sizes. Naturally pre-sorted deposits can be found in rivers and stream beds.
Gravel has a specific meaning in both Civil Engineering and Geology. In both cases it is related to the diameter of the grains which the soil is composed of.Gravels are composed of grains of sizes within the range 2 mm to 60 mm.Coarse sand = 0.6 - 2mmFine gravel = 2 - 6 mmMedium gravel = 6 - 20 mmCoarse gravel = 20 - 60 mmCobbles = 60 - 200 mmSource of data:British Standards Institution (1990) BS 1377-2:1990 -Soils for civil engineering purposes. Classification tests. Milton Keynes, BSI.
Gravel is Inorganic
Yes and also can be found in bedrock
Bedrock
The solid rock that underlies loose material, such as soil, sand, clay, or gravel.
It is usually called bedrock. When bedrock is very close to the surface it is often referred to as ledge.
Concrete
No. They can only pick up grass, dirt, sand, gravel, etc.
No. Humus is organic matter, and formed over the years as living organisms (mostly plants) die and decompose in the soil. It is about 58% carbon, by weight. Bedrock can decompose, too, but it never becomes humus. Depending on the type of bedrock, it breaks down into sand, silt, gravel and clay minerals. Limestone bedrock may dissolve.
If composting follows proper procedure, then it'll be the organic matter called humus in 21 days to a year. The amount of time depends on the turning. A minimum of a turn each day should give the desired results in less than a month.But this assumes that bedrock and gravel will be left to natural weathering processes. However, mechanical means of pulverizing bedrock and gravel would be faster than breaking compostable materials down into humus, for use as a soil amendment, fertilizer or mulch.
Gravel is made by crushing rock and sorting the result into different sizes, generally by screening. Your pea gravel is one of the screening products. There are several rock-crushing systems, and these give a different range of sizes in the product. There are hammer mills, rod mills, 'rod and cone' mills, and so on. A gravel producer would choose his process according to need. In many parts of the country, merely sorting the river gravels will be a suitable process - provided the source rocks are themselves suitable.
Alberta, Canada GC1R5CM The Slate Rock and Gravel Company (Traditional Cache) in Alberta, Canada created by 32_Hawkeye and his two Bam Bams The Slate Rock and Gravel Company A cache by 32_Hawkeye and his two Bam Bams Message this owner
Plucking is the removal of pieces of rock from a bedrock face that is in contact with glacier ice.
Gravel is made by crushing rock and sorting the result into different sizes, generally by screening. Your pea gravel is one of the screening products. There are several rock-crushing systems, and these give a different range of sizes in the product. There are hammer mills, rod mills, 'rod and cone' mills, and so on. A gravel producer would choose his process according to need. In many parts of the country, merely sorting the river gravels will be a suitable process - provided the source rocks are themselves suitable.