Sydney Sandstone 
    As part of our studies this year in Earth Science, we will learn more about the three  
    main classes of rock - igneous, sedimentary, and metamorphic rock. This past year  
    I had the opportunity to visit Sydney Australia. During my visit, I was able to view 
    one of the most unique and spectacular type of sedimentary rock known as Sydney
    Sydney sandstone is the common name for Sydney Basin Hawkesbury Sandstone. It 
    was historically known as Yellowblock, a sedimentary rock named after the
    Hawkesbury River found north of Sydney where this sandstone is very common.
    Sydney sandstone dates back millions of years ago to the Triassic Period. The ripple 
    marks in this sandstone formed from the ancient river that brought the grains of sand
    and are distinctive and easily seen.This led geologists to conclude that the sand comes
    from rocks formed between 500 to 700 million years ago. Sydney sandstone is 
    composed of very pure silica grains and a small amount of the iron mineral siderite,
    bound with a clay matrix. It oxidizes to the warm yellow - brown color that is 
    notable in the buildings that are constructed of it.
    Sydney sandstone is well known for its durable quality. Since Sydney sandstone formed
    the bedrock for much of this region, it was quite plentiful. It was a highly favored 
    building material, especially during the city's early years. From the late 1790's to the
    1890's, it was used particularly in many public buildings in an area of Sydney known
    as The Rocks District. These early buildings were built primarily by prisoners sent
    to develop the land of the early colony. 
    I have attached some actual pictures of Sydney sandstone that I took on my visit.
    I hope that you will learn some more about the features of sandstone as you take
    a closer look at these pictures of Sydney.