Materials

True.  Gunpowder also known as black powder is a mixture of charcoal, sulfur and potassium nitrate (saltpeter).  The charcoal and sulfur act as fuels and the saltpeter acts as an oxidizer. Sugar could also be used as the fuel instead of charcoal. A traditional ratio of the ingredients would be about 15:3:2 potassium nitrate, charcoal, and sulfur by weight.

A word on how it's made:

Charcoal pit. Image credit: sarahemcc

True. Charcoal can be made from anything containing carbon. Traditionally wood has been the raw material used to make charcoal. Wood consists of three main components: cellulose, lignin and water.  These compounds are composed almost entirely from atoms of hydrogen, oxygen and carbon.  Charcoal is made by removing the hydrogen and oxygen in the wood while leaving just the carbon.

The Egyptians could have been building structures out of concrete if they had only known the secret to making hydraulic cement.  In the early 19^th century, a bricklayer named Joseph Aspdin in Leeds, England first made Portland cement by burning powdered limestone and clay in his kitchen stove. He named it Portland cement because of its similarity to Portland stone, a type of building stone that was quarried on the Isle of Portland in Dorset, England.

For the sake of simplicity, we have lumped the preferred materials for making stone tools into two broad categories; flint-like and obsidian. The flint-like materials (such as chert) are mainly made from Silicon dioxide (SiO2) which is also known as silica.

Chert formations, Pindus mountains Greece(source: candiru)

Our ancestors discovered that certain stones were very hard and, when broken, they formed very sharp edges.   These were logically used to produce cutting tools such as knife blades, arrowheads, axe heads and scrapers.  Geologists have refined classification of these various stones into categories such as flints, cherts, jaspers, chalcedonies, agates, quartz, obsidian, etc.  For the purposes of simplicity it is easy to lump them into two broad categories: Flint-like and obsidian. 

Interesting use of concrete for construction  (source: seier+seier)

Concrete is the most often used construction material of the modern world.  It is simple and economic to make and if the Egyptians had known the secret they could have made it 4000 years ago. To make concrete, first you need to make the cement (or mortar) that holds the concrete together. 

The Romans did this by burning limestone (which is mostly calcium carbonate CaCO₃) to create something called quick lime (calcium oxide CaO). Burning isn't quite the right term because "to burn" usually indicates an oxidation process which involves the "chemical union of oxygen with any substance".  What actually happens in a lime kiln is that the temperature of the limestone is increased to a point above its dissociation temperature.  The earliest lime kilns were really just layers of wood and limestone stacked together and lit like a giant bonfire.  So it is easy to see why it is called burning limestone when it really isn't.