Thursday, March 5, 2020


Cabochon with Azurite
You know how some of the minerals we use to create cabochons contain metals as an integral part of their makeup, like Azurite Cu₂, and Malachite Cu₂CO₃ (OH)₂.in which copper is part of their chemical makeup. Yet there are times when a metal is side-by-side with a mineral in a slab and that situation allows you to make some unique cabs.

My experiences in working with materials that contain metal is all over the board.  For example, the Azurite above has a hardness Mohs rating of 3.4 to 5 and Copper comes in at 3. However, if the material is in matrix, the harness of the matrix must also be taken into consideration.  With the mixes pictured below including the copper and epidote are wildly different with the epidote coming in at 6-7 on the hardness scale making it very difficult to avoid undercutting and creating a very difficult situation when it comes to polishing.
Scientifically, when you get a slab that has metals and minerals, here's what you're dealing with:

METAL- (Naturally occurring) consists of a single atomic element, like iron, copper, etc.
MINERAL - a combination of several elements and is generally crystalline, some of which can be processed into metal.
Here are a few mineral/metal combinations (and not-exactly rocks) you'll probably deal with in your cab shop:

COPPER -  A Metal
For example, check out this nifty copper cabochon with an epidote matrix (according to the vendor I purchased it from) has the copper peeking through it.
Copper and Epidote
 I've heard that this kind of specimens can sometimes have quartz in it, which would have lightened its look a bit, but all in all, I like the blue-green

TIGER IRON - Mineral & Iron Oxide
However, this Tiger Iron cab? Not exactly. 
Tiger Iron

The first time I saw a slab of Tiger Iron, I thought it was a very poor quality of Tiger Eye. But I was wrong.

Tiger Iron is a separate kind of mineral that combines Tiger Eye and Hematite in random patterns. Hematite itself, is a form of Iron Oxide which is where the "Iron" in Tiger Iron comes from. Depending on the amount of Hematite vs Tiger Eye, it can be very attractive. However, I prefer a lot more Tiger Eye than Hematite, so this isn't a favorite among my cabochons. The dark overwhelms the chatoyance. I see this from time to time at rock shows, but if I'm doing the buying, I'll get straight Tiger Eye any day.

PYRITE  - Mineral

Pyrite in Quartz
I admit I love this cab!  It's quartz with pyrite  embedded in it. Because of the orange in the quartz and the shapes of the markings, it looks a lot to me like a magical fire. I wasn't able to catch the flash from the pyrite in a picture, but it's very impressive in person.

The Pyrite is a mineral (Iron Sulfide) and it's also known as "Fool's Gold". In some settings, like this, it actually looks more like the Iron it contains than gold, but if you've seen pyrite crystals, you understand where the name originated.

Tin Oxide in Quartz

RUTILE - A Mineral

 When I first started admiring Rutilated Quartz, I thought that the different colors of the thin lines meant that they were different materials. Not so. According to, Rutile (TiO2) comes in Blood red, brownish yellow, brown-red, yellow, greyish-black, black, brown, bluish or violet.

Oxides are actually found in many stones. In rutilated quartz, the rutiles  can be made of tin oxide.   That's the same stuff in the white paste lifeguards at the beach smear on their noses to prevent sunburn. More importantly, in its dry form, it makes a wonderful lapidary polish.

Do you have any inclusions that you want to identify as either metal or mineral? Send me the information and a picture and I'll see what I can do to help you identify it.

Until next time,

Your Lapidary Whisperer,


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