This is the month of spring. The Passover happened during this month and it is considered the first month of the spiritual year.
The Hebrew month of Nisan is evening March 25th - April 24th
Nisan is the beginning of the spiritual new year. New beginnings are typically not beautiful. They can be messy, appear immature and frankly -- it is usually unclear what they will become. New beginnings are in the infant stage and need nurturing to grow. Fresh beginnings often include redemption of the old, because God is the God of making all things new. Look for areas of new growth and redemption happening in your life throughout the month of Nisan.
This is a season of spiritual growth. Growth is a vital part of life. Take time to cultivate growth through spiritual practices as God calls you and draws you. He will show you the where and how - He is the Sonlight that produces growth in your life as you respond to Him.
You are called to rest in hope no matter how dark the world grows. Where darkness and sin abound, Grace abounds more. (Romans 5:20) Often things will appear to die before they begin to grow. Pay attention to places that seem dead and begin to speak life over those areas. This applies not only in your own life, but in the world at large. Use your mouth to speak beautiful resolutions to dark matters and spread HOPE as you move through life.
The stones represent passover: Black Obsidian for night and the shadow of death. Gray Agate is the twilight and "hope" of the new that is coming. White Howlite is for the light that dawned and protection of God over His people.
An interesting tidbit: According to one tradition, the three patriarchs of the Jewish people—Abraham, Isaac and Jacob —all were born and passed away in the month of Nisan.