Introduction
During an identification session, Lucid allows you to choose any question (that is, a feature and its states) in its list at any time. However, “stepping” through the key in a structured and sensible way will make your task of identification easier. The Lucid4 Player provides various options for making the task of mineral identification easier. For instance, you can view images of features and states to help make a choice between states. You can also ask the Player to determine the best feature to look at next, to have the best chance of reducing the list of Minerals (Entities) Remaining, or you can make a comparison between two or more minerals. For a comprehensive description of the options available in the Lucid Player, either go to the Help section (accessed within the Lucid Player) or go to the main Lucid web site – www.lucidcentral.org
Familiarity with the specimen – You will be more proficient in using a Lucid key if you first become familiar with the main features and states in the key. Then, when you inspect the mineral sample you wish to identify, you will be able to recognise some of the important features that you can select in the key. Briefly reviewing these before you start will make it easier for you to proceed through the identification.
Note and use distinctive features – In any key, some mineral entities may possess particularly distinctive features. Use of these may allow the mineral to be keyed out in a very few steps. At the very least, starting with particularly distinctive or striking features for the first character states selected may quickly reduce the list of Entities Remaining.
Answer easy features first – Browse the list of Features Available and address those features easiest to distinguish first. The principles of dichotomous keys, in which the couplets must be answered in a pre-set order, are very familiar to some key users who often automatically apply these principles to a matrix key. Although Lucid lists the features of a key in an initial sequence in the opening window, this does not mean that the features must be selected in that order. You can select any feature from any position in the list. Always start by browsing the list of Features Available for obvious features that you can quite quickly answer, as opposed to getting stuck on the first one. Lucid is designed to overcome problems associated with difficult and obscure features.
Choosing multiple states – Always choose multiple states (i.e., more than one state of a feature) if you are uncertain which state is the correct one to choose for a particular specimen. Lucid is designed to allow you to choose as many states as you require from any one feature. Within the program’s logic, these states will be connected by an “or” link. This will cause Lucid to search for all minerals with any of the states you select. As a general rule, if you are unsure which of two or more states your specimen has, then choose them all: that way, you can be sure that your target mineral will remain in Entities Remaining.
Finding the best feature to address next – When you have dealt with all the obvious features, use Lucid’s “Best” function to suggest the best remaining feature. The Lucid Player has two “Best” modes, Find Best and Sort Best.
1. Find Best – in the Lucid Player, clicking the Best button 
will cause the Player to move to and open the best available feature. Next Best 
and Previous Best 
buttons on the toolbar allow navigation through the Features list, if you have difficulty in addressing the feature nominated. If the list of entities in Entities Remaining changes after choosing a feature as suggested by Best, you should click the Best button again to recalculate the next best feature to address.
2. Sort Best – Sort Best will reorder the Features Available list so that features are sorted from best to worst, in terms of the likelihood of making a unique identification. After selecting Sort Best, scan the top of the list for features that you can answer most easily.
What if no mineral entities remain? – This will happen sooner or later in one of your Lucid sessions. If no minerals are listed in the Entities Remaining window, then it simply means that no minerals in the database match the selection of states you have made. Several explanations are possible, but some of the most common are:
- You have made an error in one or more states that you have selected. This is the most likely error for the situation in which no minerals remain.
- The mineral may be undescribed, or a rare mineral not included in the key. Clearly, Lucid cannot identify the specimen because its features are not represented in the key’s data tables.
- The key author may have made an error when constructing the key. This is unlikely, but it can happen. If, after carefully checking all the features and states and checking that the specimen you are attempting to identify would be expected to be included in the key, then a key construction error may be present.
Whichever of the above situations is suspected, carefully review your chosen features, and determine which ones you are uncertain about. Try unselecting uncertain states one by one to see what effect each has. One or more minerals may move back into the Entities Remaining window. In difficult cases, you may need to “play” with the key, adding or deleting states progressively to try to find the best matching mineral.
What if several minerals remain? – Never assume that you will always end up with one mineral remaining. Some minerals in the key may be very hard to differentiate, except when using difficult or obscure features. Therefore, after you have selected all the relevant Feature-states that you are able to, and still have several minerals remaining in the Entities panel, at least you will be much closer to an identification than you otherwise would have been. However, the Lucid player now allows you to try another option that may help you identify your specimen. This is the “Differences” function that can be accessed via the icon, situated on the top menu bar.
Clicking on Differences opens a panel that shows a list of minerals that have not been discarded. You can then select a feature from the drop-down list of features for which there is at least one mineral that has a state that differs from the others. The list of features is based on the degree to which they differ between the remaining minerals; the features associated with the greatest difference between species being at the top of the list. Note the list also includes numeric features. Choosing the characters highest on the list and most easily recognised should help you make an identification, or at least reduce the short list.
Checking the result – At this point, whether you have made a preliminary identification, or still cannot make a clear identification, check the other information provided in the key (such as notes, descriptions, and images) provided for the mineral you initially identified or for the remaining minerals. Getting a possible name for a mineral from a key is not the end of an identification. You may have made errors, or you may have a mineral that is not in the key. In these cases, the key may have provided you with the wrong name. The associated information will often give you a good indication of whether the answer you came to is correct or not.