Is Roxberry Puddingstone Granite

The silt is a mixture of rock flour and the residue of ash left from early volcanic eruptions.

Is roxberry puddingstone granite. The roxbury conglomerate also informally known as roxbury puddingstone is a name for a rock formation that forms the bedrock underlying most of roxbury massachusetts now part of the city of boston the bedrock formation extends well beyond the limits of roxbury underlying part or all of quincy canton milton dorchester dedham jamaica plain brighton brookline newton needham and dover. Roxbury puddingstone is a sedimentary conglomerate comprising a fine grained matrix or silt the pudding within which are inclusions of rock mostly rounded granite. The individual round pebbles can still be seen. They are the various types of rock that existed in the area at that time including volcanic rocks granite and quartzite.

Wikipedia says puddingstone also known as either pudding stone or plum pudding stone is a popular name applied to a conglomerate that consists of distinctly rounded pebbles whose colors contrast sharply with the color of the finer grained often sandy matrix or cement. Massachusetts designated roxbury puddingstone also called roxbury conglomerate as the official state rock in 1983. The gravel was laid down in the beds of rivers hundreds of years ago. This is a native sandstone inlaid with granite pebbles and fragments of quartz and then metamorphisized into something hard enough to build with.

The roxbury puddingstone is a massive ediacaran clast supported pebble and cobble conglomerate that occurs within the brookline member of the roxbury conglomerate that is exposed around boston massachusetts region. This conglomerate is composed of a grey feldspathic sand matrix and well rounded pebbles and cobbles of quartzite granite felsite and quartz monzonite. The rest of the boston basin area is composed of cambridge argillite mattapan volcanic complex and dedham granite. Roxbury puddingstone also known as roxbury conglomerate is the state rock of massachusetts existing as the sedimentary bedrock covering of much of the geographical area known as the boston basin.

The roxbury sits in the middle of a suite of rocks that includes granite found in dedham and muddy slates that occur in braintree. Note that roxbury puddingstone is in fact unique to boston but there are other types of puddingstone in the world. Historic roxbury puddingstone true native stone. Roxbury puddingstone is ancient river gravel which has cemented into hard rock by natural mineralization.

One of the most beautiful and interesting local historic materials found in the greater boston built environment is what is called roxbury puddingstone. In some places gray to green lava flows abut the puddingstone indicating that some of the volcanoes were active with molten rock flowing off their slopes.