Rock Identification Guide

Are you a rockhound or a rock collector? Do you enjoy cutting stones into cabochons or facet gemstones into unique shapes that sparkle and delight?

If you answered yes to any of these questions then you’re bound to come across a rock, crystal, or gemstone that you can identify. So, what do you do?

Some collectors will find an appraiser while others will spend time online looking for an image matching what they have.

To solve this problem, I put together an exhaustive list of rocks and gemstones with all of the identifying characteristics laid out in an easy-to-read and implemented way.

Rock Identification Tests and Tools

You’ve spent the time and effort digging these beautiful stones out of the ground but do you know what you have? Rock hounds contact me every week asking for assistance with identifying a rock, crystal, or mineral.

Some inherit the collection while others build their collection by attending rock and mineral shows and purchasing their favorite specimens.

Here is a list of tools I use for identifying rocks and there’s a list of gemstones that you can click on. Each gemstone has its own page that will assist you with identifying it on your own.

As always, if you need help identifying your rocks and minerals then contact me directly.

Jewelers Loop and Tweezers

A 10x-powered loop and a nice pair of tweezers can go a long way in identifying rocks and gems. The loop allows you to see inside the stones assuming they’re transparent. Once you have visibility into the stone you’ll start to understand what natural inclusions look like and what synthetic inclusions look like.

This allows you to quickly determine which direction to go in when you need additional details to make an accurate identification.

Gemstone Microscope

This instrument comes in handy when you need to see the finer inclusions inside of the gemstone. If you’re not appraising gemstones and your focus is on rock and mineral specimens then you probably don’t need this.

One cool activity you can do is find a piece of druzy quartz or a micro specimen and put it under the microscope. It’s like navigating through an alien world.

Key Features

• 10X-15X-30X-45X super widefield magnification settings
• Super widefield sharp clear erect stereo images
• Pillar stand w/ both incident & transmitted halogen lights
• Adjustable lighting intensities with separate controls
• Trinocular port for adding a photo or video capability

Here’s a great seller if you’re looking for a fairly priced microscope.

Polariscope

You’ll need a polariscope to determine if the gem or mineral is single or double-refractive. This is a very easy test to perform but the stone will be to be transparent or translucent. If you shine a light through it and you don’t see light being admitted back to your eye then the test will not work.

Refractive Index

Most of the gems and minerals you’ll be working with will have a refractive index so you’ll need to become proficient in taking an RI reading from the machine.

Occasionally, you’ll run into the issue of not having a flat surface to work with.  In this instance, you’ll need to leave the top of the refractometer open and hold the rounded stone with your hand.  Hopefully, you can pull a reading off of the gauge.

Specific Gravity

Specific gravity is a unitless number describing how heavy a mineral is compared to equal volumes of water. For example, if a mineral is three times as dense as water, it’ll have a specific gravity of three. This is useful because while two minerals might be the same size, they’ll each have a different specific gravity.

If you want to determine the specific gravity of your stone like a pro, you’ll need to invest in a higher-end scale.  The OHAUS Density Determination Kit is the one gemologists use.

Rock Identification Chart

These are extremely helpful because you can work your way through all of the stones quickly because they’re structured in a grid-like layout. There are a couple of people providing these but I don’t have a great resource at this time. Maybe I’ll build my own and give them away for free…