Logicspren wil vary the light they radiate based on certain stimuli. For example, if you make the Light leak from the gemstone at a controlled rate, the spren will alternate dimming and brightening in a regular pattern... When the gemstone is tapped with certain metals, the light will also change states from bright to dim.

I have been writing a list of all the metals mentioned and their effects on fabrials. Now to figure out their associations with Mistborn...

• Zinc: Stronger manifestation of spren (pg 103)
• Brass: Withdrawal/lesser manifestation of spren (pg 103)
• Bronze: Warning signal (pg 116)
• Pewter: Augmentation, expressing attribute in force (pg 126)
• Tin: Diminish attributes (pg 141)
• Steel/Iron: changes polarity (pg 141)
• Iron: Attracts elements to itself (pg 151)