English: This sample is from an exploratory drill core in a kimberlite pipe in northwestern Russia.

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Sample description by a Russian diamond exploration geologist (I'm not 100% sure who it was):

Kimberlite xenotufobreccia (Kimberlite xenotuff breccia), Osetinskaya Pipe, Verkhotinskoye Field

Crystallolithoclastic structure. Total content of clastic material in rock is about 80%, including 40% xenogenic quartz crystalloclasts, aleurolite lithoclasts, and carbonaceous rocks. Kimberlite clastic material (40%) is represented by autholiths, fragments of microlithic melilite kimberlites and also of saponite pseudomorphs of olivine of the first and second generation. Cement of breccia (about 20% of rock) is represented by saponite-carbonaceous aggregate with the admixture of iron hydroxides. Lithoclasts of melilite kimberlites contain in the matrix up to 30% of replaced melilite and also single signs of nepheline. The content of diamond-satellite minerals is very low. Among them there are predominant chrome-spinellide, and pyrope with chrome-diopside as rare signs.

[Note: the Russian term "aleurolite" is close to "siltstone".]

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I've not encountered an age for this kimberlite pipe, but another pipe in the same field intrudes upper Neoproterozoic rocks and is overlain by Middle Devonian rocks.

Geologic unit: Osetinskaya Pipe, Verkhotinskoye Field (Verkhotinsky Field), Arkhangelskaya Diamond Province

Locality: Osetinskaya Pipe, north-northeast of the town of Arkhangelsk, Arkhangelsk Region, east of the White Sea, northwestern Russia