This video features a dendritic talc (also known as soapstone). The location is from southwestern Montana (USA). Note that this sample has been cut by a saw (causing the flat surfaces and related cutting lines on the surfaces). The distinctive black color, of the delicately branching textures in this soapstone, are manganese oxide minerals—called dendrites. The dendrites are not fossils, and dendrites are not the tiny roots of plants (within the rock). Notice that the dendrites are more concentrated in some areas, and less in other areas, of the soapstone.

This soapstone weathers brown, and is often sold commercially to stone carvers and hobbyists for creating figurines. Also, I have seen this soapstone sold as polished cabochons in jewelry, featuring the distinctive dendritic patterns. However, soapstone would make the worst material for jewelry, because it would be very easily damaged. Essentially, it would be extremely vulnerable to scratches and wear if it came in contact with almost any solid material (including sand and dirt).

Talc is a very soft mineral, and can be scratched by a fingernail (talc is rated as only one on Mohs hardness scale of ten--a fingernail has a hardness of 2.5-3.0). Talc is called soapstone, because it is so soft that the surfaces can be easily worn, and feels somewhat slippery or greasy when rubbed. It often feels soft like the surface of a bar of soap—especially along flat surfaces (obviously, it will not lather or clean things, like actual soap).

Note that some types of talc are slightly harder than one on Mohs hardness scale—if traces of other minerals or elements are found within a talc deposit. However, because of the very soft nature of talc, I have seen pure soapstone deposits quarried by chainsaws in Washington State (USA). Similar to minerals, the hardness of wood is variable by either soft or hard wood types. Obviously, most wood is much softer that most minerals (the Janka scale is applied to wood hardness—and is a different scale than the geologically oriented Mohs hardness scale for minerals). Note that the hardened steel found in most chain saws (normally designed to cut wood), have a Mohs hardness of at least 5.5. So a chain saw (with steel cutting teeth) would be quite effective at cutting talc. However, if the talc deposit contains areas with other minerals, it would not be appropriate for quarrying that way. Talc is often found within layers of gneissic rocks. Most minerals in gneiss have a hardness of five to seven on Mohs scale (from common minerals as feldspar, quartz, and mafic minerals). Diamond-tip saws are meant to cut rock and minerals (diamond has a hardness of ten on Mohs hardness scale).

Note that talc often contains various asbestos minerals (sometimes as much as 40% or more asbestos). Asbestos is considered a carcinogen in some countries and may be regulated. Exposure to talc dust from cutting, grinding, quarrying is hazardous to health.

Hello Rock People! This is Dave the Geology dude! Identification notes for this rock are below in this text. Don't forget that Geology isn't rocket science--it's Rock Science! Please "like" and subscribe to this YouTube channel!

Identification information for this rock:
1) environment: talc is associated with mafic and ultramafic rocks
2) Shape/cleavages: talc forms rocks that often break into one or two, semi-flat and semi-parallel sides. There is one bad cleavage--which is a semi-distinct layering structure in talc. It will preferentially split or cleave along this layering structure--but often not very cleanly/easily.
3) Color--talc can be greenish, pinkish, grayish, or light-grayish, or dark-grayish colors.
4) density--density is similar to most other rocks
5) hardness--it is only 1 on Mohs' hardness scale. It will not scratch glass (but may leave a powder on the glass because the glass instead will be abrading the rock--as you try to scratch the glass with it). Your fingernail will scratch the surface of talc, and talc will feel somewhat slippery like soap--if you rub it with your fingers
6) acid reactivity: will not react to acid contact
7) luster--talc may have a nonmetallic pearly, silky, or resinous luster.
8) often confused with gypsum--because gypsum also is a very soft mineral that can be easily scratched by a fingernail. However, the surfaces of gypsum don't feel soapy like talc (gypsum feels more like plastic or bone). And gypsum has three cleavages--two of these usually are fairly easy to see (but talc has only one bad cleavage). Note: If a talc rock sample is handled too much (such as in a classroom)--it may result in fairly rounded surfaces over the whole rock (therefore, difficult to see the cleavage layers--although, it should feel very soapy, if it is rounded)

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