The short answer is no, halite will not scratch glass.
Each material has a different Mohs hardness from one another, with halite being the softer material at 2-2.5, and glass being the harder at 5.5-7.
Let’s take a look at each mineral in detail to see why this is the case.
Can Halite Scratch Glass? (Let’s Learn More)
The History of Glass
Our first topic will be glass and its history.
Since our ancestors could walk upright, they have used glass in addition to stone and wooden tools.
There has been evidence to suggest that obsidian, a naturally occurring glass formed via volcanic activity, was that very glass.
The events surrounding the first manufactured glass are a bit uncertain, with the actual inventor’s name lost to history.
However, several historical accounts do point out that the first glass manufacturers appeared in the Palestinian area.
Even the ancient-Roman historian, Pliny the Elder, wrote that glass making started on the Phoenician coast, now known as Lebanon.
The technique was then further developed by both the ancient Egyptians and Mesopotamians around 1500BC.
Considering glass blowing wasn’t practiced until the 1st century BC by the Syrians, our ancient predecessors could only make simple glass beads, small bottles, and other precious treasures used by the very rich and royalty.
Back then, glass was as precious as jewels today, as only the rich could afford it at the time.
Later on, during the Roman Empire, glass production, specifically glass blowing, became a widespread practice.
Could early versions of glass have marks put into by halite?
Seeing as how most early forms of glass were made from silica sand, or silicone dioxide (SiO2), it would’ve had a Mohs hardness of 7, meaning halite couldn’t scratch it.
Then what about the earliest of glasses, obsidian?
Considering its 5-6 hardness, halite wouldn’t be able to scratch it either.
Let’s fast forward to modern times.
You could probably find an example of glass just by looking around you.
A window, the screen on your phone, or even a shiny decoration hanging above your kitchen sink, glass is just about everywhere in our lives.
The most common form today is by far soda-lime glass.
This type is used to make food jars, beer bottles, simple drinking glasses, or even the door for a glass cabinet.
Similar to ancient forms of glass, soda-lime has a high silica sand content, ranging from 71-75%, and other elements such as 10-15% lime (CaO), 12-16% sodium bicarbonate (Na2O), with the addition of small amounts of dye to give the finished product some color.
Other kinds of commonly used glass include crystal and borosilicate.
Some examples of crystal glass are wine glasses, fancy dishware, vases, and decorative ornaments such as chandeliers.
This type of glass has less silica sand content in comparison to soda-lime, around 54-65%, which is mixed with 13-15% alkali oxide and many other oxides as well.
Borosilicate glass is used for many “heatproof” applications in laboratories, as well as containment for chemicals in the pharmaceutical industry.
With its 70-80% silica sand content, this type of glass also has 4-8% sodium and potassium oxide, 2-7% aluminum oxide, and 7-13% boron trioxide, hence the name.
Could these modern forms of glass be scratched by halite?
Even though most glass that we use today may be a bit softer than what our ancient ancestors used, around 6-7 of the Mohs hardness scale, it isn’t soft enough to be scratched by the 2-2.5 halite has.
The softer nature of modern glass is due to the desire to make it more malleable, so that multiple shapes can be made from it on demand.
Now we’ll look at halite.
It’s more common name is “rock salt,” due to its simple chemical formula, sodium chloride (NaCl).
In fact, the very name “halite” essentially means “salt” in ancient Greek.
Halite can be colorless; light blue, white, purple, orange, pink, red, gray, dark blue, or even yellow, depending on whatever other minerals are within.
This mineral will form inside sedimentary rocks via evaporation of salty lake water or seawater.
It can be found in multiple areas across the US and Canada within underground beds that stretch from the Michigan Basin all the way to the Appalachian Basin of western New York.
Halite can also be located within the Khewra salt mine near Islamabad, Pakistan.
Another structure that Halite forms is a salt dome, a structure that can be seen from high up in the air.
It forms when masses of salt are “squeezed up” from salt beds underneath via the weight of overlying rock, thus causing mobilization of the halite.
Various other minerals can also be found in salt domes, such as sulfur, sylvite, anhydrite, and gypsum.
Multiple regions across the world are known to have salt domes, such as the Gulf coasts of Texas, Germany, Denmark, Spain, the Netherlands, Iran, the state of Louisiana, and Romania.
Halite has been in use by humans for thousands of years for spicing up food as well as for its preservation.
It has also been used in the past as a form of currency in many early bartering systems, and in conquest to make enemy lands barren for growing crops.
Aside from sprinkling a bit of seasoning on a huge variety of edible dishes, halite or rock salt is also used to de-ice roads during cold seasons, and weeding efforts to prevent certain plants from leeching nutrients from valuable food crops.
So, in conclusion, the mineral halite cannot scratch glass, whether it’s an ancient piece of Egyptian jewelry or a bottle that you’d find in your recycling bin.