A headstone, tombstone, or gravestone is a stele or marker, usually stone, that is placed over a grave. In most cases, it has the deceased’s name, and date of death inscribed on it, along with a personal message, or prayer. Most headstones NYC made over the last few centuries are made of a few types of rock: marble, slate, and granite are the big three. Sometimes you run into darker stones made of gabbro, maybe a few sandstone markers, but especially in more recent monuments, marble and granite (and other plutonic rocks) rule the roost. Older graveyards tend to use rock that was available locally, so they can be variable. A lot of the old gravestones are made of readily available limestone. They’re attractive but they are not the best choice if you want your marker to last long.
It turns out that making your gravestone (or any monument) from materials like marble is not a good idea for longevity. Rocks can break down two ways: physically and chemically. Physical weathering is the toll put on rocks by processes like frost/ice splitting, abrasion (from things hitting it), plant roots, decompression at the surface and more. Chemical weathering are reactions that occur when the rock interacts with water, air, and acids. The two types of weathering work together to make the tallest mountain into nothing more than a pile of sand given enough time. Rocks are made of several minerals and some of these minerals are more liable to breaking down at the earth’s surface than others.
If we wanted to rank common headstone minerals that have been widely used to create gravestone memorials in terms of how quickly they weather, it would look something like this (from most to least weatherable):
- Calcite (Marble is almost 100% calcite)
- Olivine (Gabbro)
- Plagioclase feldspar (common in gabbro, granite and almost every igneous rock)
- Pyroxene (common in gabbro)
- Amphibole (common in diorite to granite)
- Biotite (common in granite)
- Orthoclase feldspar (common in granite)
- Muscovite (somewhat common in granite)
- Quartz (really common in granite, quartzite, sandstone)
Calcite is terrible when it comes to withstanding the ravages of chemical weathering. This is why the old gravestones of the Midwest are barely legible because acid rain created by factory pollution has dissolved a lot of the calcite in the limestone and marble gravestones. Even more hardy minerals like plagioclase feldspar, found in everything from gabbro to granite, can be susceptible to breaking down into clays when they react with acidic water.
What rock types might withstand the ravages of chemical weathering?
Granite and sandstone are excellent choices for catholic headstones as they contain stable minerals like quartz and orthoclase. However, physical weathering can hit them hard. Sandstone might be mostly quartz (depending on what kind you select), but sandstone is really just sand grains cemented together. Water can alter the cement or get into cracks between the grains, and when it freezes it can split! This is what happens in headstones made of slate, where the prominent parting known as cleavage can allow water into the rock to split it apart. Who knew that water was such an enemy of rocks?
What are you going to do if you want your headstone to last forever?
- When it comes to footstones for graves, it is important to use non-reactive metals, so yes, make your headstone out of solid gold and it would last a long time (or as long as it takes for someone to steal it and melt it down).
- Second would be something made entirely of what we call “resistant” minerals that are resistant to chemical and physical weathering. There are a bunch of uncommon minerals like zircon, monazite and sphene that can take a beating and persist. However, making a gravestone out of these minerals might mean a very, very small marker.
- What more common minerals might work? Well, the two best might be garnet and quartz. Now, depending on your desire to stand out in a cemetery, trying to make an average size solid garnet or quartz marker would be hard. Typically these minerals don’t form enormous blocks that can be carved into headstones. However, quartz is the primary constituent of quartzite .
Quartzite is a metamorphic rock made from heating up sandstone under pressure. it fuses all those quartz sand grains together into an interlocking network of quartz. All the weakness between the grains is removed and instead you get an almost solid block of quartz. Quartzite would be highly resistant to chemical weathering because it’s quartz. And because it lacks a lot of space for water to sneak in, very resistant to physical weathering as well. Make your tombstone out of quartzite and you’re looking at a rock for the ages.