FMF - Friends of Minerals Forum, discussion and message board

[Pete Richards]

This is a Mineral Forum.

Minerals are naturally-occurring chemical compounds with nearly constant compositions and properties. Quartz is a mineral, for example. It is sometimes clear, sometimes smoky, sometimes purple (variety amethyst), but it always has the basic composition SiO2, a hardness of 7 on the Mohs scale, a hexagonal/trigonal crystal structure (though this may only be visually evident in well-formed crystals), specific optical indices of refraction, a density of 2.65, etc.

The study of minerals is a serious undertaking, and requires some investment of time and resources on your part, but can be extremely rewarding. We suggest you explore the following post: Asking: "What is this? / Where is it from?" , which is located in A general guide for using the Forum with some rules and tips

Rocks are made up of minerals. Some are made up of only one mineral. Limestone, for example, is usually made up of the mineral calcite. Other rocks are made up of several to many minerals. Granite is a rock usually made up of quartz, one or more of the feldspar group of minerals, one or more micas, and perhaps other minerals. In a granite, the composition of each of these minerals is nearly constant, but the appearance and properties of the granite can vary dramatically depending on the relative abundance of the minerals present and the size of their grains.

So the study of rocks involves many different approaches than the study of minerals. For this site, if a rock poses interesting mineral issues, it is appropriate. Otherwise it is not. This is not our area of expertise.

Many things that newcomers are interested in fall more or less into three categories:

• things they have picked up, for example, in a stream or beside a lake on a camping trip,
• curious stuff their Granddad or Aunt had, or
• pretty or interesting things they have purchased at a garage sale or a mineral and gem show.

For the most part, the first group represents rocks, not minerals, and the processes that have brought them to where they were obtained pretty much obscure anything meaningful that we can tell you about them. The relevant observations are hidden inside the rock and can only be revealed by breaking it open. Usually that’s not what folks want to do.

The second group may include rocks, minerals, or other objects. The usual problem here is that there is no historical information to indicate where and when an object was obtained. If this information is available, then the identity of the object is likely to be there as well, in which case you don’t need us, except perhaps to comment on value, which we do not do.

The third group typically consists of man-made objects that are neither rocks nor minerals, because rocks and minerals are objects, the composition or appearance of which by definition were not influenced by human intervention. Most inexpensive ornamental objects and gems in inexpensive jewelry are man-made. Found objects that belong to group 1 are often man-made or man-modified as well. Examples include attractive glassy materials that turn out to be industrial slags, melted glass or plastic or metal from some ancient burn pile, and pieces of glass rounded by wave action on an ocean beach. These are not minerals, and are things we cannot comment on in any useful way.

If you’ve read this far, we invite you to explore this website in a lot more detail and get a sense of its structure and its purpose. Again, particularly pay attention to Asking: "What is this? / Where is it from?" and A general guide for using the Forum with some rules and tips but also explore widely. Perhaps then you can see how your object fits with our purpose (or not), and we can help you answer your questions.

A final comment: many posts use pictures to show the object the poster is seeking information about. Pictures that are out of focus or improperly lit are of little use and tend to provoke frustration on the part of potential responders, not a feeling of helpfulness.