I started my life as a sea shell in a warm ancient shallow sea. When I
died my shell joined many others in the ooze at the bottom of the sea.
Layers and layers of ooze built up and the weight of the ooze above forced
the water out and I slowly turned into a sedimentary
rock called limestone.
Time passed and the limestone was pushed up and became land.
Time passed until hot rocks from deep beneath the earth rose up and cooked
me at a low temperature. I didn't melt but my crystals grew bigger,
denser and needle-like and most visible evidence of my life as a sea shell
I became a metamorphic
But I am not gone!
Crystals generally need a nucleus on which to form (like a hailstone needs
a speck of dust from which to grow).
Although you can't see my shell anymore, it's edge provided the nucleus
from which the crystals in the image grew.
If you look close you can see they still mimic the outline of my fossil
shell long gone!
The contact aureoles produced in siliceous limestones and dolomites,
called skarns or calc-silicate rocks, characteristically contain
metamorphic amphiboles such as tremolite or actinolite (similar to
tremolite by green in colour). The presence of tremolite implies a
relatively low grade of metamorphism as tremolite breaks down to form the
pyroxene diopside in the presence of calcite and quartz at elevated
temperatures. Richterite-winchite occurs in hydrothermally metamorphosed
limestones. Magnesium-rich anthophyllites are found along contact zones of
granitic dikes intruding ultramafic rocks (those rich in iron and
magnesium). Tremolite and Actinolite are members of the asbestos group of
source: Earth Science Australia collection