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What Is A Mineraloid? Minerals vs. Mineraloids & Examples
Cos'è un Mineraloid
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What Is A MineraloidA mineraloid is a natural substance that shares similarities with minerals but doesn’t meet every official, geological requirement to be a mineral. Mineraloids are often organic substances and notably lack a crystal structure, but they’re commonly used as gemstones.

Most people know gemstones as beautiful, often colorful and sparkling treasures, but what is a gemstone? Definitions vary, but many sources describe gemstones as minerals used for adornment, sometimes mentioning organic gemstones

Why does knowing the difference between minerals and mineraloids matter? If you’re studying gemology, knowing the different properties helps with identification. For casual gemstone lovers, this knowledge can help you shop smarter, practice proper gemstone care, and know the fascinating history behind your favorite jewels.

This guide will teach you everything you need to know about mineraloids vs. minerals and which gemstones are actually mineraloids.

First, we have to establish some base knowledge about minerals. 

what is a mineraloid

What Is A Mineral?

Every mineral is broadly classified by its chemical composition and internal structure. Some can have the same composition but different internal structures, making them different minerals. For example, diamond and graphite are both made of carbon atoms arranged differently.

In geology, the mineral definition has five parts, or requirements to be met:

  1. Formed naturally (not man-made)

  2. Solid (not liquid or gas)

  3. Inorganic (not formed by or made from living organisms)

  4. Structure of organized, repeated atom patterns that forms crystals (put simply: crystallinity)

  5. Definite chemical composition (not accounting for inclusions)

The last two may be a bit confusing. Let’s do a quick science lesson to explain.

Breaking it down to basics, we start with one or more elements, like silicon or oxygen for example. When elements combine through a chemical reaction, we get compounds (or substances) like silicon dioxide. 

In minerals, the elements combine in the same, ordered arrangement every time that mineral forms. For example, every quartz mineral has the same arrangement of silicon and oxygen (silica) inside. 

Inclusions that sneak in during formation can create different colored versions of the same mineral. For quartz, inclusions like iron and aluminum can create citrine or amethyst.

You can imagine inclusions like extra flavors added to a cake. Cakes have a set ratio of key ingredients that are essential to it coming out right, like a mineral’s chemical elements. Added ingredients like nuts, fruits, or chocolate are equivalent to inclusions in a mineral.

Clearly, there are lots of definitions and terms pertaining to minerals, but where do all these terms come from?

Who Decides On Mineral Terminology?

The official terminology for minerals comes from the International Mineralogical Association (IMA). The IMA was formed in 1958 in part to create standard, consistent names and definitions for minerals. 

Founded in 1958, the IMA is relatively modern, started almost 30 years after gemology began. The organization recognizes new minerals annually, having approved a total 5,780 minerals as of January 2022

Now that you know the requirements of a mineral, what is a mineraloid by simple definition? 

What Is the Difference Between a Mineral and a Mineraloid?

Mineraloids are mineral-like, but don’t meet every mineral requirement. As such, mineraloids can vary a bit more than minerals. 

However, all mineraloids (except pearl) are amorphous, meaning they don’t have a crystal structure. Additionally, most mineraloids form under similar conditions: low pressure, low temperature, and close proximity to Earth’s surface.

The difference between minerals and mineraloids gets tricky for certain minerals, though — namely, biogenic minerals

Something is “biogenic” when it’s made of an organism (like plants or animals) or by an organism. Biogenic minerals are similar to other minerals but formed by organisms.

Many minerals are silicates formed in rocks, but some organisms like algae and sea sponges produce silica or incorporate it into their structure. The resulting silicate is a biogenic mineral.

What about rocks? Rocks aren’t minerals either, but rather combinations of multiple minerals and/or mineraloids. Plus, rocks can be gemstones, too! Some examples are tiger’s eye and lapis lazuli. You might see minerals intermixed throughout a rock, forming a “matrix” gemstone, or filling the hollow inside of a rock (e.g. geodes). 

As you can see, there’s quite a bit of cross-over to keep track of. Next, we’ll make things a bit more organized by going over the general categories of mineraloids.

30 CTSANCIENT ROMAN GLASS SG-1320 SIMPLYGEMSImage: ancient Roman glass

Types of Mineraloids

There aren’t official classifications of mineraloids, but most fall under one of four categories: 

  • Glass: Hard, inorganic solid with random atom arrangement and no crystal structure (often from cooling too quickly)

  • Animal-Based: Formed from parts of an animal (shell, skeleton, tissue, etc.)

  • Plant-Based: Made from secretions (e.g. tree sap) or parts of a plant, often that have fallen off

  • Liquid: Fluids with definite composition that can crystallize into minerals at certain temperatures

The animal-based and plant-based categories can be combined into the broader “organic” category. The liquid category is small, only covering two substances.

Our categories above don’t cover every mineraloid, though. Opal, for instance, isn’t organic, liquid, or glass, so why is opal a mineraloid? It lacks a crystal structure and has an “n” in its chemical formula, meaning part of its composition (amount of water) varies from one opal to the next.

Each category can also have different subtypes. Glass may be volcanic glass or impact glass (formed from meteorite impact), to name a couple. Animal-based mineraloids may be created by the animal (e.g. pearls) or from their remains (e.g. ammolite).

Examples of Mineraloids

Below, we’ll go over each mineraloid, including which category of mineraloid (if any) it falls into.  

amber gemstone mineraloid

  • Amber: Plant-based; Fossilized plant resin excreted from ancient pine trees that hardens into a translucent, natural plastic, often with insects or plants inside.

canadian ammolite gemstone mineraloid

  • Ammolite: Animal-based; Iridescent, fossilized shell of the extinct mollusk ammonite, composed of calcium carbonate and trace minerals.

coral gemstone specimen mineraloid

  • Coral (Precious Coral): Animal-based; Often brightly colored, branching, exoskeleton shed by coral polyps and composed of calcium carbonate.

black jet gemstone mineraloid

  • Jet: Plant-based; Type of coal formed when decomposing wood is buried and fossilized under extreme heat and pressure. Is coal a mineraloid, then? Yep!

libyan desert glass mineraloid

  • Libyan Desert Glass: Glass; Impact glass formed in sandy areas when the extreme heat and pressure of a meteorite impact melts surrounding soil and rocks into liquid, which cools too rapidly to form crystals.

  • Mercury: Liquid; Classified by some mineralogists as a mineraloid for its definite chemical composition and ability to crystallize into a mineral at -38.8℃.

obsidian spheres mineraloid

  • Obsidian: Glass; Dark, volcanic glass formed when flowing lava cools too rapidly for crystals to form; Called “apache tears” when rounded and pebble-like.

Opal gemstone mineraloid 

  • Opal: Amorphous, hardened, hydrated silica gel with varying levels of water.

pearl gemstone mineraloid

  • Pearl: Animal-based; Crystalline, organic mineraloid composed of concentric layers of calcium carbonate (nacre) and formed by certain mollusks when irritants get into its shell.

  • Pumice: Glass; Lightweight, porous, volcanic glass formed when lava explodes out and the rapid decrease in temperature and pressure creates bubbles that freeze in place as it solidifies.

tektite gemstone pendant mineraloid example

  • Tektite: Glass; Group of impact glass mineraloids (including moldavite) formed when meteorite impact explosion causes material to rapidly melt, fly into the air, then fall back to Earth, cooling too quickly to form crystals.

  • Tuff: Rhyolitic volcanic ash compacted together from pressure, containing glassy shards and a crust of other mineral crystals. 

  • Water: Like mercury, a liquid classified by some mineralogists as a mineraloid for its definite chemical composition and ability to crystallize into a mineral (ice) at 0℃

Wait, is ice a mineraloid? Nope, it’s a mineral! It may be surprising, but ice that forms naturally on its own (not in your freezer) is technically a mineral!

mineraloid ammolite shell pendants

Mix Up Your Style With Mineraloid Gemstones!

After all that, you’re set to crush a mineraloid vs. mineral quiz, that’s for sure! More importantly, you have the knowledge to become a confident, savvy gemstone buyer.

Mineraloids may not be as straightforward or abundant as minerals, but that doesn’t make them any less beautiful as gemstones. Plus, many mineraloids can offer us a connection with the vast and fascinating history of Earth — and the cosmos beyond!

Those looking for a wholly one-of-a-kind gem with a story to tell will certainly fall in love with any mineraloid gem.

Want to explore the array of beautiful mineraloids and minerals? Find your favorite gems today!.

Cos'è un Mineraloid Un mineraloide è una sostanza molto simile a un minerale, ma non dimostra cristallinità. Le sue composizioni chimiche variano rispetto a minerali specifici che hanno intervalli accettabili specifici. Un mineraloide può apparire come un vero minerale all'esterno ma all'interno, manca la struttura chimica ordinata per essere considerato un minerale. Per comprendere ulteriormente le considerazioni relative al fatto che un determinato materiale sia un minerale, deve soddisfare i seguenti cinque requisiti:

  1. Si verifica o si sviluppa in modo naturale;
  2. Non è organico;
  3. È solido;
  4. Ha una struttura ordinata; e
  5. Ha una composizione chimica definita.

Per distinguere ulteriormente un minerale da un mineraloide, un minerale ha una forma cristallina, il che significa che ha una struttura atomica ordinata. Al contrario, un mineraloide ha una forma amorfa, quindi ha una struttura atomica non organizzata e non può mai formare cristalli in un dato stato.
Cos'è un Mineraloid

Esempi di Mineraloid

Ecco alcuni degli esempi di mineraloidi le loro caratteristiche:

  • Opale - È una silice idrata amorfa che ha una "n" nella sua formula chimica. Ciò significa che la quantità di acqua presente varia e non può mai essere strutturata o riparata.
  • Ossidiana - È una roccia ignea che si solidifica rapidamente dopo la fusione, il che rende i suoi atomi a malapena in grado di muoversi e quindi non in grado di formare una struttura atomica strutturata.
  • Perla - Anche se considerato da alcuni come un minerale, sarebbe meglio considerarlo come un mineraloide poiché i suoi cristalli sono uniti attraverso un materiale organico e i suoi componenti non hanno una proporzione definita.
  • Tektite - Un tipo di vetro naturale che si forma a causa dell'impatto di un asteroide. Man mano che un asteroide arriva sulla Terra così rapidamente, qualsiasi materiale colpito da esso si scioglierà rapidamente. Allo stesso tempo, la temperatura del materiale fuso si scioglierà e solidificherà rapidamente senza formare cristalli.
  • Acqua - Una sostanza naturale inorganica che ha una composizione chimica strutturata. Tuttavia, non è solido al suo stato normale e si cristallizza anche se sottoposto a temperatura di zero gradi. Queste proprietà lo rendono un mineraloide
  • Ambra - È una resina di piante fossili che si trova principalmente nelle rocce sedimentarie di tutto il mondo. È spesso tagliato come una pietra preziosa a causa della sua natura dura e fragile. Sembra un minerale ma in realtà non ha una struttura interna ordinata.


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