Pitchstone facts for kids
Pitchstone is a fascinating type of volcanic rock. It looks like dark glass and forms when hot, melted rock cools down very quickly. You can find it in many colors like brown, red, green, or even black. It's a strong rock that resists wearing away over time.
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What is Pitchstone?
Pitchstone is a special kind of volcanic rock. It forms when lava (melted rock on the Earth's surface) or magma (melted rock underground) cools down very fast. This quick cooling stops crystals from growing large. It makes the rock look like glass. Geologists call rocks like this "volcanic glass". Pitchstone is also known as a "felsic" rock. This means it has a lot of silica, a common mineral.
Its Glassy Look and Feel
Because pitchstone cools so quickly, it often has a shiny, resinous look. It can look like hardened tree sap. Sometimes, it can even look silky! If you were to break a piece of pitchstone, it would likely show a special type of break. This is called a "conchoidal fracture". It means it breaks with smooth, curved surfaces. This is similar to how thick glass breaks.
Pitchstone can come in many colors. It might be solid brown, red, green, gray, or black. Sometimes, it has streaks or mottled patterns. This makes each piece unique. Even though it's mostly glassy, some pitchstones contain tiny crystals. These are called phenocrysts. When it has these crystals, it's called a vitrophyre.
Where Can We Find Pitchstone?
Pitchstone is an extrusive rock. This means it forms when lava flows out onto the Earth's surface. Then it cools there. Because it's so tough, pitchstone is very resistant to erosion. This is why you can often see it forming tall, strong ridges in landscapes.
A famous example is the pitchstone ridge of An Sgùrr. This is on the Isle of Eigg in Scotland. Scientists believe this impressive ridge formed long ago. Lava flowed into a valley and then hardened. Over millions of years, the softer rocks around it wore away. This left the tough pitchstone standing tall.
Pitchstone Through History
People have used pitchstone for thousands of years! On the Isle of Arran, also in Scotland, ancient communities discovered this useful rock. From the Mesolithic period (Middle Stone Age) through the Neolithic period (New Stone Age) and into the Early Bronze Age, pitchstone was a valuable material.
During the Mesolithic period, people on Arran used pitchstone. They made tools and other items. Later, in the Neolithic and Early Bronze Age, pitchstone became even more important. Items made from Arran pitchstone, or the raw rock itself, were transported. They were traded across different parts of Britain. This shows how much people valued its strength. It also shows how well it could be shaped.
