Key
Ore Minerals
The following are some tips on how I identify the different ore minerals. Remember to look carefully at the samples, look at as many samples as possible, and find the characteristics for each mineral that help YOU identify it. What works for me may not work for you.
1. Sulfur: I identify this mineral primarily by the bright yellow color and the rotten egg smell. There isn’t any other common mineral that looks like sulfur.
2. Pyrite: Often (not always) has a cubic habit and striations. Pyrite is harder than glass and has a gold metallic luster. A mineral that is similar is Chalcopyrite but its color is more yellow gold and looks slightly tarnished. Additionally, it’s softer than glass.
4. Chalcopyrite: Yellow gold, no preferred habit, softer than glass and appears tarnished.
5. Sphalerite: Sub-metallic luster. This is primarily what I use to ID it. It also has a blackish/yellowish/brownish color, streaks pale yellow-brown, and has MANY directions of cleavage. I often don’t rely on the cleavage to ID it however…I use color and luster.
6. Galena: Silver metallic. Often very shiny. VERY dense (ore of lead). Cubic habit with excellent cleavage in 3 directions
8. Realgar: Reddish in color but often appears orangeish due to the fact that it commonly (if not always) occurs with another mineral (Orpiment) that is yellow in color. It often covers the surface of a host rock and cleavage is NOT easy to see. A mineral similar to Realgar is Cinnabar. Cinnabar is more of a rosy red color (kind of like a stick of big red chewing gum) and it has excellent cleavage.
10. Cinnabar: Rosy red in color, grows on the surface or in fractures of a host rock, and has excellent cleavage.
11. Stibnite: Long needle like crystals that are very shiny silver (metallic). Excellent cleavage.
12. Bornite: This mineral has the name of “peacock ore” due to the many iridescent colors it has. If you catch this mineral in the light you often will see iridescent purples, blues, greens and golds. Some students have said it looks like an oil slick on water.
13 &14. Hematite: This mineral can have many different appearances. The Micaceous Hematite is glittery/silver while the Ocherous Hematite looks like a rusted piece of metal or rock. The reason they look different is due to how oxidized the mineral is. The defining characteristic of any Hematite is the reddish-brown streak. When you streak the micaceous varity often a glittery streak will be left. This is just the crystals themselves being left behind. If you wipe the glitter off you will see the true streak.
15. Limonite: this is a yellowish brown earthy mineral that looks like a dirty/muddy rock. It has a mustard yellow streak which can be used to identify it.
16. Magnetite: A black mineral that most the time looks metallic but doesn’t have to. The key to magnetite is the blackish grey streak and the fact that it is STRONGLY magnetic.
17. Chromite: this is a glittery black mineral that has a brownish streak. It is distinguishable from Micaceous Hematite by the color (black vs silver) and the shade of the streak. Also, Chromite is harder to streak than Hematite.
18. Bauxite: This is the ore of aluminum and is actually composed of three different minerals. The distinguishing feature of bauxite is the color (white and tan) and the texture. It is made up of a bunch of little spheres all stuck together.
20. Pyrolusite: This mineral is a manganese oxide that covers the surface of rocks that are exposed in dry climates. The mineral is black in color and given enough time, Pyrolusite will cover the entire surface, coating the rock with black. Before the surface of the rock is completely covered, Pyrolusite will have the appearance of a fern that has been pressed onto the rocks surface. It looks so much like a fern that often people think it is a fossil.
22. Smithsonite: This is a mineral that appears in layers and is tan to white in color. Because of the environment it forms in, it often will have small holes or pockets in the structure.
23. Rhodochrosite: This mineral is light pink to dark pink in color (always pink) and will often form nice crystals with good cleavage.
24. Malachite: Green mineral that can appear as a coating on the surface of a rock or can be distinguishable crystals. Good cleavage when crystals are present. Can occur with Azurite but doesn’t have to.
25. Azurite: Blue mineral that can appear as a coating on the surface of a rock or can be distinguishable crystals. Good cleavage when crystals are present. Most the time Malachite occurs with Azurite.
26. Barite: Barite has several forms. Cubes, blades or sheaths. It will vary in color from yellow to white and can have a brownish red oxidation associated with it. It will always have good cleavage and is very dense. This is often what I use to distinguish this mineral…density and cleavage.
27. Celesite: I use the color for the primary ID on this mineral. It is often a sky blue or a celestial blue color with some red mixed in (oxidation). It occurs as long bladed crystals and has great cleavage.
28. Gypsum: Massive gypsum is soft! It is Moh’s mineral 2 so you can break it apart with your fingernail. Additionally it is white to pink in color and has a greasy luster.
29. Fluorite: This is a mineral that can come in a variety of colors so don’t use that to distinguish it. Fluorite has the habit of cubes, diamonds or triangles, it has fracture and a hardness of 4 (it is also a Moh’s mineral).
31. Halite: This is salt. A great way to ID it is taste (though not a good idea in the lab where you don’t know how much acid was dropped on the sample). Another way to id it is that it looks like a piece of ice. It has a cubic habit, perfect cleavage in 3 directions and is transparent.
35. Colemanite: This mineral is white in color and comes in a massive crystalline form with very small crystals (good cleavage) or radiating needles from a central point.
36. Ulexite: This is a white, translucent mineral and the crystals look like a bunch of fibers that have been bound together. The “fibers” all run in the same direction showing good cleavage and a unique texture.