Among gravel, sands, silt and clay, these grains have different sizes. Except their original materials, do they appear different colours due to different abilities of reflection?
The question is yes.
Take a specimen of basalt and compare it with a gabbro. Both are chemical almost identical and basic igneous rocks. Their mineral assemblage consists of pyroxene, plagioclase and some olivine plus magnetite. The fine-grained basalt is dark and the coarse-grained gabbro shows a bright mottled outward appearrance.
Sandstone sensu lato may contain quartz, feldspar and muscovite. All of them have a bright mineral color. A claystone or siltstone although being enriched in muscovite takes a darker rock color. In some cases it may be due to the presence of organic material which also is of minor particle size.
There are exceptions from the rule as you consider "black sands". These sandstones contain often dark mafic minerals such as ilmenite and magnetite. In this sedimentary rocks the preponderance of the black minerals governs the overall rock color.
H.G.Dill
The question is yes.
Take a specimen of basalt and compare it with a gabbro. Both are chemical almost identical and basic igneous rocks. Their mineral assemblage consists of pyroxene, plagioclase and some olivine plus magnetite. The fine-grained basalt is dark and the coarse-grained gabbro shows a bright mottled outward appearrance.
Sandstone sensu lato may contain quartz, feldspar and muscovite. All of them have a bright mineral color. A claystone or siltstone although being enriched in muscovite takes a darker rock color. In some cases it may be due to the presence of organic material which also is of minor particle size.
There are exceptions from the rule as you consider "black sands". These sandstones contain often dark mafic minerals such as ilmenite and magnetite. In this sedimentary rocks the preponderance of the black minerals governs the overall rock color.
H.G.Dill
Zhanchao Shao
You may want to look at:
https://www.google.com/search?sxsrf=ACYBGNS_e8x6QFbcvqORonk6eULuLhubhA%3A1572996853619&source=hp&ei=9QbCXY6SI4S8sQWX3L7oBw&q=multiple+scattering+reflection+transmission+particle+size+distribution+refraction&oq=multiple+scattering+reflection+transmission+particle+size+distribution+refraction&gs_l=psy-ab.12...12671.12671..14732...0.0..0.209.209.2-1......0....2j1..gws-wiz.wmB7_X-ueQ4&ved=0ahUKEwjO4ML1ndTlAhUEXqwKHReuD30Q4dUDCAs
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https://www.google.com/search?sxsrf=ACYBGNSH4BTOziBYFHQRb3ekArCRdwqw1A%3A1572997008121&ei=kAfCXezxBoTIsQX3n5fACQ&q=color+multiple+scattering+reflection+transmission+particle+size+distribution+refraction&oq=color+multiple+scattering+reflection+transmission+particle+size+distribution+refraction&gs_l=psy-ab.12...69739.73626..75811...0.2..0.172.1278.0j9......0....1..gws-wiz.......0i71j35i304i39j33i10.ZdyxeDXUT2w&ved=0ahUKEwjs-Zq_ntTlAhUEZKwKHffPBZgQ4dUDCAo
yes, grain size also impact over color of matter due to light phenomenon
With equal mineralogical composition and dry material, what change is Lightness: finer grains absorb less, and therefore they look clearer. In the CIEL*a*b* color space I did not find significant changes in a* or b* values. But if you have different results, I'd like to see them.
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