a. Min. [f. ACID + -IC.]
1. Applied by Dana to that element in a ternary compound mineral, which forms an oxygen, sulphur, or other salt, with a basic element; e.g., the silicon in silicate of lime. See quotation under ACIDIFIC.
1880. Dana, Mineral., Introd. 16. In some classes of compounds only part of the oxygen serves to unite the acidic element to the basic.
2. Abounding in an acidic element, usually silicon.
1877. Green, Phys. Geol., ii. § 5. 47. So the Crystalline rocks can be divided … into the Highly Silicated or Acidic rocks.
1878. Lawrence, trans. Cotta, Rocks Classified, 120. The acidic rocks … are distinguished by a felspar richer in silica.
1879. Rutley, Study of Rocks, iv. 34. Both acidic and basic rocks are known in some instances to have emanated, etc.
